text: /**
   * @license
   * Copyright 2016 Google Inc. All rights reserved.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  (() => {
      var _a, _b, _c;
      /* Symbols for private properties */
      const _blockingElements = Symbol();
      const _alreadyInertElements = Symbol();
      const _topElParents = Symbol();
      const _siblingsToRestore = Symbol();
      const _parentMO = Symbol();
      /* Symbols for private static methods */
      const _topChanged = Symbol();
      const _swapInertedSibling = Symbol();
      const _inertSiblings = Symbol();
      const _restoreInertedSiblings = Symbol();
      const _getParents = Symbol();
      const _getDistributedChildren = Symbol();
      const _isInertable = Symbol();
      const _handleMutations = Symbol();
      class BlockingElementsImpl {
          constructor() {
              /**
               * The blocking elements.
               */
              this[_a] = [];
              /**
               * Used to keep track of the parents of the top element, from the element
               * itself up to body. When top changes, the old top might have been removed
               * from the document, so we need to memoize the inerted parents' siblings
               * in order to restore their inerteness when top changes.
               */
              this[_b] = [];
              /**
               * Elements that are already inert before the first blocking element is
               * pushed.
               */
              this[_c] = new Set();
          }
          destructor() {
              // Restore original inertness.
              this[_restoreInertedSiblings](this[_topElParents]);
              // Note we don't want to make these properties nullable on the class,
              // since then we'd need non-null casts in many places. Calling a method on
              // a BlockingElements instance after calling destructor will result in an
              // exception.
              const nullable = this;
              nullable[_blockingElements] = null;
              nullable[_topElParents] = null;
              nullable[_alreadyInertElements] = null;
          }
          get top() {
              const elems = this[_blockingElements];
              return elems[elems.length - 1] || null;
          }
          push(element) {
              if (!element || element === this.top) {
                  return;
              }
              // Remove it from the stack, we'll bring it to the top.
              this.remove(element);
              this[_topChanged](element);
              this[_blockingElements].push(element);
          }
          remove(element) {
              const i = this[_blockingElements].indexOf(element);
              if (i === -1) {
                  return false;
              }
              this[_blockingElements].splice(i, 1);
              // Top changed only if the removed element was the top element.
              if (i === this[_blockingElements].length) {
                  this[_topChanged](this.top);
              }
              return true;
          }
          pop() {
              const top = this.top;
              top && this.remove(top);
              return top;
          }
          has(element) {
              return this[_blockingElements].indexOf(element) !== -1;
          }
          /**
           * Sets `inert` to all document elements except the new top element, its
           * parents, and its distributed content.
           */
          [(_a = _blockingElements, _b = _topElParents, _c = _alreadyInertElements, _topChanged)](newTop) {
              const toKeepInert = this[_alreadyInertElements];
              const oldParents = this[_topElParents];
              // No new top, reset old top if any.
              if (!newTop) {
                  this[_restoreInertedSiblings](oldParents);
                  toKeepInert.clear();
                  this[_topElParents] = [];
                  return;
              }
              const newParents = this[_getParents](newTop);
              // New top is not contained in the main document!
              if (newParents[newParents.length - 1].parentNode !== document.body) {
                  throw Error('Non-connected element cannot be a blocking element');
              }
              // Cast here because we know we'll call _inertSiblings on newParents
              // below.
              this[_topElParents] = newParents;
              const toSkip = this[_getDistributedChildren](newTop);
              // No previous top element.
              if (!oldParents.length) {
                  this[_inertSiblings](newParents, toSkip, toKeepInert);
                  return;
              }
              let i = oldParents.length - 1;
              let j = newParents.length - 1;
              // Find common parent. Index 0 is the element itself (so stop before it).
              while (i > 0 && j > 0 && oldParents[i] === newParents[j]) {
                  i--;
                  j--;
              }
              // If up the parents tree there are 2 elements that are siblings, swap
              // the inerted sibling.
              if (oldParents[i] !== newParents[j]) {
                  this[_swapInertedSibling](oldParents[i], newParents[j]);
              }
              // Restore old parents siblings inertness.
              i > 0 && this[_restoreInertedSiblings](oldParents.slice(0, i));
              // Make new parents siblings inert.
              j > 0 && this[_inertSiblings](newParents.slice(0, j), toSkip, null);
          }
          /**
           * Swaps inertness between two sibling elements.
           * Sets the property `inert` over the attribute since the inert spec
           * doesn't specify if it should be reflected.
           * https://html.spec.whatwg.org/multipage/interaction.html#inert
           */
          [_swapInertedSibling](oldInert, newInert) {
              const siblingsToRestore = oldInert[_siblingsToRestore];
              // oldInert is not contained in siblings to restore, so we have to check
              // if it's inertable and if already inert.
              if (this[_isInertable](oldInert) && !oldInert.inert) {
                  oldInert.inert = true;
                  siblingsToRestore.add(oldInert);
              }
              // If newInert was already between the siblings to restore, it means it is
              // inertable and must be restored.
              if (siblingsToRestore.has(newInert)) {
                  newInert.inert = false;
                  siblingsToRestore.delete(newInert);
              }
              newInert[_parentMO] = oldInert[_parentMO];
              newInert[_siblingsToRestore] = siblingsToRestore;
              oldInert[_parentMO] = undefined;
              oldInert[_siblingsToRestore] = undefined;
          }
          /**
           * Restores original inertness to the siblings of the elements.
           * Sets the property `inert` over the attribute since the inert spec
           * doesn't specify if it should be reflected.
           * https://html.spec.whatwg.org/multipage/interaction.html#inert
           */
          [_restoreInertedSiblings](elements) {
              for (const element of elements) {
                  const mo = element[_parentMO];
                  mo.disconnect();
                  element[_parentMO] = undefined;
                  const siblings = element[_siblingsToRestore];
                  for (const sibling of siblings) {
                      sibling.inert = false;
                  }
                  element[_siblingsToRestore] = undefined;
              }
          }
          /**
           * Inerts the siblings of the elements except the elements to skip. Stores
           * the inerted siblings into the element's symbol `_siblingsToRestore`.
           * Pass `toKeepInert` to collect the already inert elements.
           * Sets the property `inert` over the attribute since the inert spec
           * doesn't specify if it should be reflected.
           * https://html.spec.whatwg.org/multipage/interaction.html#inert
           */
          [_inertSiblings](elements, toSkip, toKeepInert) {
              for (const element of elements) {
                  // Assume element is not a Document, so it must have a parentNode.
                  const parent = element.parentNode;
                  const children = parent.children;
                  const inertedSiblings = new Set();
                  for (let j = 0; j < children.length; j++) {
                      const sibling = children[j];
                      // Skip the input element, if not inertable or to be skipped.
                      if (sibling === element || !this[_isInertable](sibling) ||
                          (toSkip && toSkip.has(sibling))) {
                          continue;
                      }
                      // Should be collected since already inerted.
                      if (toKeepInert && sibling.inert) {
                          toKeepInert.add(sibling);
                      }
                      else {
                          sibling.inert = true;
                          inertedSiblings.add(sibling);
                      }
                  }
                  // Store the siblings that were inerted.
                  element[_siblingsToRestore] = inertedSiblings;
                  // Observe only immediate children mutations on the parent.
                  const mo = new MutationObserver(this[_handleMutations].bind(this));
                  element[_parentMO] = mo;
                  let parentToObserve = parent;
                  // If we're using the ShadyDOM polyfill, then our parent could be a
                  // shady root, which is an object that acts like a ShadowRoot, but isn't
                  // actually a node in the real DOM. Observe the real DOM parent instead.
                  const maybeShadyRoot = parentToObserve;
                  if (maybeShadyRoot.__shady && maybeShadyRoot.host) {
                      parentToObserve = maybeShadyRoot.host;
                  }
                  mo.observe(parentToObserve, {
                      childList: true,
                  });
              }
          }
          /**
           * Handles newly added/removed nodes by toggling their inertness.
           * It also checks if the current top Blocking Element has been removed,
           * notifying and removing it.
           */
          [_handleMutations](mutations) {
              const parents = this[_topElParents];
              const toKeepInert = this[_alreadyInertElements];
              for (const mutation of mutations) {
                  // If the target is a shadowRoot, get its host as we skip shadowRoots when
                  // computing _topElParents.
                  const target = mutation.target.host || mutation.target;
                  const idx = target === document.body ?
                      parents.length :
                      parents.indexOf(target);
                  const inertedChild = parents[idx - 1];
                  const inertedSiblings = inertedChild[_siblingsToRestore];
                  // To restore.
                  for (let i = 0; i < mutation.removedNodes.length; i++) {
                      const sibling = mutation.removedNodes[i];
                      if (sibling === inertedChild) {
                          console.info('Detected removal of the top Blocking Element.');
                          this.pop();
                          return;
                      }
                      if (inertedSiblings.has(sibling)) {
                          sibling.inert = false;
                          inertedSiblings.delete(sibling);
                      }
                  }
                  // To inert.
                  for (let i = 0; i < mutation.addedNodes.length; i++) {
                      const sibling = mutation.addedNodes[i];
                      if (!this[_isInertable](sibling)) {
                          continue;
                      }
                      if (toKeepInert && sibling.inert) {
                          toKeepInert.add(sibling);
                      }
                      else {
                          sibling.inert = true;
                          inertedSiblings.add(sibling);
                      }
                  }
              }
          }
          /**
           * Returns if the element is inertable.
           */
          [_isInertable](element) {
              return false === /^(style|template|script)$/.test(element.localName);
          }
          /**
           * Returns the list of newParents of an element, starting from element
           * (included) up to `document.body` (excluded).
           */
          [_getParents](element) {
              const parents = [];
              let current = element;
              // Stop to body.
              while (current && current !== document.body) {
                  // Skip shadow roots.
                  if (current.nodeType === Node.ELEMENT_NODE) {
                      parents.push(current);
                  }
                  // ShadowDom v1
                  if (current.assignedSlot) {
                      // Collect slots from deepest slot to top.
                      while (current = current.assignedSlot) {
                          parents.push(current);
                      }
                      // Continue the search on the top slot.
                      current = parents.pop();
                      continue;
                  }
                  current = current.parentNode ||
                      current.host;
              }
              return parents;
          }
          /**
           * Returns the distributed children of the element's shadow root.
           * Returns null if the element doesn't have a shadow root.
           */
          [_getDistributedChildren](element) {
              const shadowRoot = element.shadowRoot;
              if (!shadowRoot) {
                  return null;
              }
              const result = new Set();
              let i;
              let j;
              let nodes;
              const slots = shadowRoot.querySelectorAll('slot');
              if (slots.length && slots[0].assignedNodes) {
                  for (i = 0; i < slots.length; i++) {
                      nodes = slots[i].assignedNodes({
                          flatten: true,
                      });
                      for (j = 0; j < nodes.length; j++) {
                          if (nodes[j].nodeType === Node.ELEMENT_NODE) {
                              result.add(nodes[j]);
                          }
                      }
                  }
                  // No need to search for <content>.
              }
              return result;
          }
      }
      document.$blockingElements =
          new BlockingElementsImpl();
  })();
  
  var _createClass = function () { function defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } } return function (Constructor, protoProps, staticProps) { if (protoProps) defineProperties(Constructor.prototype, protoProps); if (staticProps) defineProperties(Constructor, staticProps); return Constructor; }; }();
  
  function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }
  
  /**
   * This work is licensed under the W3C Software and Document License
   * (http://www.w3.org/Consortium/Legal/2015/copyright-software-and-document).
   */
  
  (function () {
    // Return early if we're not running inside of the browser.
    if (typeof window === 'undefined') {
      return;
    }
  
    // Convenience function for converting NodeLists.
    /** @type {typeof Array.prototype.slice} */
    var slice = Array.prototype.slice;
  
    /**
     * IE has a non-standard name for "matches".
     * @type {typeof Element.prototype.matches}
     */
    var matches = Element.prototype.matches || Element.prototype.msMatchesSelector;
  
    /** @type {string} */
    var _focusableElementsString = ['a[href]', 'area[href]', 'input:not([disabled])', 'select:not([disabled])', 'textarea:not([disabled])', 'button:not([disabled])', 'details', 'summary', 'iframe', 'object', 'embed', '[contenteditable]'].join(',');
  
    /**
     * `InertRoot` manages a single inert subtree, i.e. a DOM subtree whose root element has an `inert`
     * attribute.
     *
     * Its main functions are:
     *
     * - to create and maintain a set of managed `InertNode`s, including when mutations occur in the
     *   subtree. The `makeSubtreeUnfocusable()` method handles collecting `InertNode`s via registering
     *   each focusable node in the subtree with the singleton `InertManager` which manages all known
     *   focusable nodes within inert subtrees. `InertManager` ensures that a single `InertNode`
     *   instance exists for each focusable node which has at least one inert root as an ancestor.
     *
     * - to notify all managed `InertNode`s when this subtree stops being inert (i.e. when the `inert`
     *   attribute is removed from the root node). This is handled in the destructor, which calls the
     *   `deregister` method on `InertManager` for each managed inert node.
     */
  
    var InertRoot = function () {
      /**
       * @param {!Element} rootElement The Element at the root of the inert subtree.
       * @param {!InertManager} inertManager The global singleton InertManager object.
       */
      function InertRoot(rootElement, inertManager) {
        _classCallCheck(this, InertRoot);
  
        /** @type {!InertManager} */
        this._inertManager = inertManager;
  
        /** @type {!Element} */
        this._rootElement = rootElement;
  
        /**
         * @type {!Set<!InertNode>}
         * All managed focusable nodes in this InertRoot's subtree.
         */
        this._managedNodes = new Set();
  
        // Make the subtree hidden from assistive technology
        if (this._rootElement.hasAttribute('aria-hidden')) {
          /** @type {?string} */
          this._savedAriaHidden = this._rootElement.getAttribute('aria-hidden');
        } else {
          this._savedAriaHidden = null;
        }
        this._rootElement.setAttribute('aria-hidden', 'true');
  
        // Make all focusable elements in the subtree unfocusable and add them to _managedNodes
        this._makeSubtreeUnfocusable(this._rootElement);
  
        // Watch for:
        // - any additions in the subtree: make them unfocusable too
        // - any removals from the subtree: remove them from this inert root's managed nodes
        // - attribute changes: if `tabindex` is added, or removed from an intrinsically focusable
        //   element, make that node a managed node.
        this._observer = new MutationObserver(this._onMutation.bind(this));
        this._observer.observe(this._rootElement, { attributes: true, childList: true, subtree: true });
      }
  
      /**
       * Call this whenever this object is about to become obsolete.  This unwinds all of the state
       * stored in this object and updates the state of all of the managed nodes.
       */
  
  
      _createClass(InertRoot, [{
        key: 'destructor',
        value: function destructor() {
          this._observer.disconnect();
  
          if (this._rootElement) {
            if (this._savedAriaHidden !== null) {
              this._rootElement.setAttribute('aria-hidden', this._savedAriaHidden);
            } else {
              this._rootElement.removeAttribute('aria-hidden');
            }
          }
  
          this._managedNodes.forEach(function (inertNode) {
            this._unmanageNode(inertNode.node);
          }, this);
  
          // Note we cast the nulls to the ANY type here because:
          // 1) We want the class properties to be declared as non-null, or else we
          //    need even more casts throughout this code. All bets are off if an
          //    instance has been destroyed and a method is called.
          // 2) We don't want to cast "this", because we want type-aware optimizations
          //    to know which properties we're setting.
          this._observer = /** @type {?} */null;
          this._rootElement = /** @type {?} */null;
          this._managedNodes = /** @type {?} */null;
          this._inertManager = /** @type {?} */null;
        }
  
        /**
         * @return {!Set<!InertNode>} A copy of this InertRoot's managed nodes set.
         */
  
      }, {
        key: '_makeSubtreeUnfocusable',
  
  
        /**
         * @param {!Node} startNode
         */
        value: function _makeSubtreeUnfocusable(startNode) {
          var _this2 = this;
  
          composedTreeWalk(startNode, function (node) {
            return _this2._visitNode(node);
          });
  
          var activeElement = document.activeElement;
  
          if (!document.body.contains(startNode)) {
            // startNode may be in shadow DOM, so find its nearest shadowRoot to get the activeElement.
            var node = startNode;
            /** @type {!ShadowRoot|undefined} */
            var root = undefined;
            while (node) {
              if (node.nodeType === Node.DOCUMENT_FRAGMENT_NODE) {
                root = /** @type {!ShadowRoot} */node;
                break;
              }
              node = node.parentNode;
            }
            if (root) {
              activeElement = root.activeElement;
            }
          }
          if (startNode.contains(activeElement)) {
            activeElement.blur();
            // In IE11, if an element is already focused, and then set to tabindex=-1
            // calling blur() will not actually move the focus.
            // To work around this we call focus() on the body instead.
            if (activeElement === document.activeElement) {
              document.body.focus();
            }
          }
        }
  
        /**
         * @param {!Node} node
         */
  
      }, {
        key: '_visitNode',
        value: function _visitNode(node) {
          if (node.nodeType !== Node.ELEMENT_NODE) {
            return;
          }
          var element = /** @type {!Element} */node;
  
          // If a descendant inert root becomes un-inert, its descendants will still be inert because of
          // this inert root, so all of its managed nodes need to be adopted by this InertRoot.
          if (element !== this._rootElement && element.hasAttribute('inert')) {
            this._adoptInertRoot(element);
          }
  
          if (matches.call(element, _focusableElementsString) || element.hasAttribute('tabindex')) {
            this._manageNode(element);
          }
        }
  
        /**
         * Register the given node with this InertRoot and with InertManager.
         * @param {!Node} node
         */
  
      }, {
        key: '_manageNode',
        value: function _manageNode(node) {
          var inertNode = this._inertManager.register(node, this);
          this._managedNodes.add(inertNode);
        }
  
        /**
         * Unregister the given node with this InertRoot and with InertManager.
         * @param {!Node} node
         */
  
      }, {
        key: '_unmanageNode',
        value: function _unmanageNode(node) {
          var inertNode = this._inertManager.deregister(node, this);
          if (inertNode) {
            this._managedNodes['delete'](inertNode);
          }
        }
  
        /**
         * Unregister the entire subtree starting at `startNode`.
         * @param {!Node} startNode
         */
  
      }, {
        key: '_unmanageSubtree',
        value: function _unmanageSubtree(startNode) {
          var _this3 = this;
  
          composedTreeWalk(startNode, function (node) {
            return _this3._unmanageNode(node);
          });
        }
  
        /**
         * If a descendant node is found with an `inert` attribute, adopt its managed nodes.
         * @param {!Element} node
         */
  
      }, {
        key: '_adoptInertRoot',
        value: function _adoptInertRoot(node) {
          var inertSubroot = this._inertManager.getInertRoot(node);
  
          // During initialisation this inert root may not have been registered yet,
          // so register it now if need be.
          if (!inertSubroot) {
            this._inertManager.setInert(node, true);
            inertSubroot = this._inertManager.getInertRoot(node);
          }
  
          inertSubroot.managedNodes.forEach(function (savedInertNode) {
            this._manageNode(savedInertNode.node);
          }, this);
        }
  
        /**
         * Callback used when mutation observer detects subtree additions, removals, or attribute changes.
         * @param {!Array<!MutationRecord>} records
         * @param {!MutationObserver} self
         */
  
      }, {
        key: '_onMutation',
        value: function _onMutation(records, self) {
          records.forEach(function (record) {
            var target = /** @type {!Element} */record.target;
            if (record.type === 'childList') {
              // Manage added nodes
              slice.call(record.addedNodes).forEach(function (node) {
                this._makeSubtreeUnfocusable(node);
              }, this);
  
              // Un-manage removed nodes
              slice.call(record.removedNodes).forEach(function (node) {
                this._unmanageSubtree(node);
              }, this);
            } else if (record.type === 'attributes') {
              if (record.attributeName === 'tabindex') {
                // Re-initialise inert node if tabindex changes
                this._manageNode(target);
              } else if (target !== this._rootElement && record.attributeName === 'inert' && target.hasAttribute('inert')) {
                // If a new inert root is added, adopt its managed nodes and make sure it knows about the
                // already managed nodes from this inert subroot.
                this._adoptInertRoot(target);
                var inertSubroot = this._inertManager.getInertRoot(target);
                this._managedNodes.forEach(function (managedNode) {
                  if (target.contains(managedNode.node)) {
                    inertSubroot._manageNode(managedNode.node);
                  }
                });
              }
            }
          }, this);
        }
      }, {
        key: 'managedNodes',
        get: function get() {
          return new Set(this._managedNodes);
        }
  
        /** @return {boolean} */
  
      }, {
        key: 'hasSavedAriaHidden',
        get: function get() {
          return this._savedAriaHidden !== null;
        }
  
        /** @param {?string} ariaHidden */
  
      }, {
        key: 'savedAriaHidden',
        set: function set(ariaHidden) {
          this._savedAriaHidden = ariaHidden;
        }
  
        /** @return {?string} */
        ,
        get: function get() {
          return this._savedAriaHidden;
        }
      }]);
  
      return InertRoot;
    }();
  
    /**
     * `InertNode` initialises and manages a single inert node.
     * A node is inert if it is a descendant of one or more inert root elements.
     *
     * On construction, `InertNode` saves the existing `tabindex` value for the node, if any, and
     * either removes the `tabindex` attribute or sets it to `-1`, depending on whether the element
     * is intrinsically focusable or not.
     *
     * `InertNode` maintains a set of `InertRoot`s which are descendants of this `InertNode`. When an
     * `InertRoot` is destroyed, and calls `InertManager.deregister()`, the `InertManager` notifies the
     * `InertNode` via `removeInertRoot()`, which in turn destroys the `InertNode` if no `InertRoot`s
     * remain in the set. On destruction, `InertNode` reinstates the stored `tabindex` if one exists,
     * or removes the `tabindex` attribute if the element is intrinsically focusable.
     */
  
  
    var InertNode = function () {
      /**
       * @param {!Node} node A focusable element to be made inert.
       * @param {!InertRoot} inertRoot The inert root element associated with this inert node.
       */
      function InertNode(node, inertRoot) {
        _classCallCheck(this, InertNode);
  
        /** @type {!Node} */
        this._node = node;
  
        /** @type {boolean} */
        this._overrodeFocusMethod = false;
  
        /**
         * @type {!Set<!InertRoot>} The set of descendant inert roots.
         *    If and only if this set becomes empty, this node is no longer inert.
         */
        this._inertRoots = new Set([inertRoot]);
  
        /** @type {?number} */
        this._savedTabIndex = null;
  
        /** @type {boolean} */
        this._destroyed = false;
  
        // Save any prior tabindex info and make this node untabbable
        this.ensureUntabbable();
      }
  
      /**
       * Call this whenever this object is about to become obsolete.
       * This makes the managed node focusable again and deletes all of the previously stored state.
       */
  
  
      _createClass(InertNode, [{
        key: 'destructor',
        value: function destructor() {
          this._throwIfDestroyed();
  
          if (this._node && this._node.nodeType === Node.ELEMENT_NODE) {
            var element = /** @type {!Element} */this._node;
            if (this._savedTabIndex !== null) {
              element.setAttribute('tabindex', this._savedTabIndex);
            } else {
              element.removeAttribute('tabindex');
            }
  
            // Use `delete` to restore native focus method.
            if (this._overrodeFocusMethod) {
              delete element.focus;
            }
          }
  
          // See note in InertRoot.destructor for why we cast these nulls to ANY.
          this._node = /** @type {?} */null;
          this._inertRoots = /** @type {?} */null;
          this._destroyed = true;
        }
  
        /**
         * @type {boolean} Whether this object is obsolete because the managed node is no longer inert.
         * If the object has been destroyed, any attempt to access it will cause an exception.
         */
  
      }, {
        key: '_throwIfDestroyed',
  
  
        /**
         * Throw if user tries to access destroyed InertNode.
         */
        value: function _throwIfDestroyed() {
          if (this.destroyed) {
            throw new Error('Trying to access destroyed InertNode');
          }
        }
  
        /** @return {boolean} */
  
      }, {
        key: 'ensureUntabbable',
  
  
        /** Save the existing tabindex value and make the node untabbable and unfocusable */
        value: function ensureUntabbable() {
          if (this.node.nodeType !== Node.ELEMENT_NODE) {
            return;
          }
          var element = /** @type {!Element} */this.node;
          if (matches.call(element, _focusableElementsString)) {
            if ( /** @type {!HTMLElement} */element.tabIndex === -1 && this.hasSavedTabIndex) {
              return;
            }
  
            if (element.hasAttribute('tabindex')) {
              this._savedTabIndex = /** @type {!HTMLElement} */element.tabIndex;
            }
            element.setAttribute('tabindex', '-1');
            if (element.nodeType === Node.ELEMENT_NODE) {
              element.focus = function () {};
              this._overrodeFocusMethod = true;
            }
          } else if (element.hasAttribute('tabindex')) {
            this._savedTabIndex = /** @type {!HTMLElement} */element.tabIndex;
            element.removeAttribute('tabindex');
          }
        }
  
        /**
         * Add another inert root to this inert node's set of managing inert roots.
         * @param {!InertRoot} inertRoot
         */
  
      }, {
        key: 'addInertRoot',
        value: function addInertRoot(inertRoot) {
          this._throwIfDestroyed();
          this._inertRoots.add(inertRoot);
        }
  
        /**
         * Remove the given inert root from this inert node's set of managing inert roots.
         * If the set of managing inert roots becomes empty, this node is no longer inert,
         * so the object should be destroyed.
         * @param {!InertRoot} inertRoot
         */
  
      }, {
        key: 'removeInertRoot',
        value: function removeInertRoot(inertRoot) {
          this._throwIfDestroyed();
          this._inertRoots['delete'](inertRoot);
          if (this._inertRoots.size === 0) {
            this.destructor();
          }
        }
      }, {
        key: 'destroyed',
        get: function get() {
          return (/** @type {!InertNode} */this._destroyed
          );
        }
      }, {
        key: 'hasSavedTabIndex',
        get: function get() {
          return this._savedTabIndex !== null;
        }
  
        /** @return {!Node} */
  
      }, {
        key: 'node',
        get: function get() {
          this._throwIfDestroyed();
          return this._node;
        }
  
        /** @param {?number} tabIndex */
  
      }, {
        key: 'savedTabIndex',
        set: function set(tabIndex) {
          this._throwIfDestroyed();
          this._savedTabIndex = tabIndex;
        }
  
        /** @return {?number} */
        ,
        get: function get() {
          this._throwIfDestroyed();
          return this._savedTabIndex;
        }
      }]);
  
      return InertNode;
    }();
  
    /**
     * InertManager is a per-document singleton object which manages all inert roots and nodes.
     *
     * When an element becomes an inert root by having an `inert` attribute set and/or its `inert`
     * property set to `true`, the `setInert` method creates an `InertRoot` object for the element.
     * The `InertRoot` in turn registers itself as managing all of the element's focusable descendant
     * nodes via the `register()` method. The `InertManager` ensures that a single `InertNode` instance
     * is created for each such node, via the `_managedNodes` map.
     */
  
  
    var InertManager = function () {
      /**
       * @param {!Document} document
       */
      function InertManager(document) {
        _classCallCheck(this, InertManager);
  
        if (!document) {
          throw new Error('Missing required argument; InertManager needs to wrap a document.');
        }
  
        /** @type {!Document} */
        this._document = document;
  
        /**
         * All managed nodes known to this InertManager. In a map to allow looking up by Node.
         * @type {!Map<!Node, !InertNode>}
         */
        this._managedNodes = new Map();
  
        /**
         * All inert roots known to this InertManager. In a map to allow looking up by Node.
         * @type {!Map<!Node, !InertRoot>}
         */
        this._inertRoots = new Map();
  
        /**
         * Observer for mutations on `document.body`.
         * @type {!MutationObserver}
         */
        this._observer = new MutationObserver(this._watchForInert.bind(this));
  
        // Add inert style.
        addInertStyle(document.head || document.body || document.documentElement);
  
        // Wait for document to be loaded.
        if (document.readyState === 'loading') {
          document.addEventListener('DOMContentLoaded', this._onDocumentLoaded.bind(this));
        } else {
          this._onDocumentLoaded();
        }
      }
  
      /**
       * Set whether the given element should be an inert root or not.
       * @param {!Element} root
       * @param {boolean} inert
       */
  
  
      _createClass(InertManager, [{
        key: 'setInert',
        value: function setInert(root, inert) {
          if (inert) {
            if (this._inertRoots.has(root)) {
              // element is already inert
              return;
            }
  
            var inertRoot = new InertRoot(root, this);
            root.setAttribute('inert', '');
            this._inertRoots.set(root, inertRoot);
            // If not contained in the document, it must be in a shadowRoot.
            // Ensure inert styles are added there.
            if (!this._document.body.contains(root)) {
              var parent = root.parentNode;
              while (parent) {
                if (parent.nodeType === 11) {
                  addInertStyle(parent);
                }
                parent = parent.parentNode;
              }
            }
          } else {
            if (!this._inertRoots.has(root)) {
              // element is already non-inert
              return;
            }
  
            var _inertRoot = this._inertRoots.get(root);
            _inertRoot.destructor();
            this._inertRoots['delete'](root);
            root.removeAttribute('inert');
          }
        }
  
        /**
         * Get the InertRoot object corresponding to the given inert root element, if any.
         * @param {!Node} element
         * @return {!InertRoot|undefined}
         */
  
      }, {
        key: 'getInertRoot',
        value: function getInertRoot(element) {
          return this._inertRoots.get(element);
        }
  
        /**
         * Register the given InertRoot as managing the given node.
         * In the case where the node has a previously existing inert root, this inert root will
         * be added to its set of inert roots.
         * @param {!Node} node
         * @param {!InertRoot} inertRoot
         * @return {!InertNode} inertNode
         */
  
      }, {
        key: 'register',
        value: function register(node, inertRoot) {
          var inertNode = this._managedNodes.get(node);
          if (inertNode !== undefined) {
            // node was already in an inert subtree
            inertNode.addInertRoot(inertRoot);
          } else {
            inertNode = new InertNode(node, inertRoot);
          }
  
          this._managedNodes.set(node, inertNode);
  
          return inertNode;
        }
  
        /**
         * De-register the given InertRoot as managing the given inert node.
         * Removes the inert root from the InertNode's set of managing inert roots, and remove the inert
         * node from the InertManager's set of managed nodes if it is destroyed.
         * If the node is not currently managed, this is essentially a no-op.
         * @param {!Node} node
         * @param {!InertRoot} inertRoot
         * @return {?InertNode} The potentially destroyed InertNode associated with this node, if any.
         */
  
      }, {
        key: 'deregister',
        value: function deregister(node, inertRoot) {
          var inertNode = this._managedNodes.get(node);
          if (!inertNode) {
            return null;
          }
  
          inertNode.removeInertRoot(inertRoot);
          if (inertNode.destroyed) {
            this._managedNodes['delete'](node);
          }
  
          return inertNode;
        }
  
        /**
         * Callback used when document has finished loading.
         */
  
      }, {
        key: '_onDocumentLoaded',
        value: function _onDocumentLoaded() {
          // Find all inert roots in document and make them actually inert.
          var inertElements = slice.call(this._document.querySelectorAll('[inert]'));
          inertElements.forEach(function (inertElement) {
            this.setInert(inertElement, true);
          }, this);
  
          // Comment this out to use programmatic API only.
          this._observer.observe(this._document.body || this._document.documentElement, { attributes: true, subtree: true, childList: true });
        }
  
        /**
         * Callback used when mutation observer detects attribute changes.
         * @param {!Array<!MutationRecord>} records
         * @param {!MutationObserver} self
         */
  
      }, {
        key: '_watchForInert',
        value: function _watchForInert(records, self) {
          var _this = this;
          records.forEach(function (record) {
            switch (record.type) {
              case 'childList':
                slice.call(record.addedNodes).forEach(function (node) {
                  if (node.nodeType !== Node.ELEMENT_NODE) {
                    return;
                  }
                  var inertElements = slice.call(node.querySelectorAll('[inert]'));
                  if (matches.call(node, '[inert]')) {
                    inertElements.unshift(node);
                  }
                  inertElements.forEach(function (inertElement) {
                    this.setInert(inertElement, true);
                  }, _this);
                }, _this);
                break;
              case 'attributes':
                if (record.attributeName !== 'inert') {
                  return;
                }
                var target = /** @type {!Element} */record.target;
                var inert = target.hasAttribute('inert');
                _this.setInert(target, inert);
                break;
            }
          }, this);
        }
      }]);
  
      return InertManager;
    }();
  
    /**
     * Recursively walk the composed tree from |node|.
     * @param {!Node} node
     * @param {(function (!Element))=} callback Callback to be called for each element traversed,
     *     before descending into child nodes.
     * @param {?ShadowRoot=} shadowRootAncestor The nearest ShadowRoot ancestor, if any.
     */
  
  
    function composedTreeWalk(node, callback, shadowRootAncestor) {
      if (node.nodeType == Node.ELEMENT_NODE) {
        var element = /** @type {!Element} */node;
        if (callback) {
          callback(element);
        }
  
        // Descend into node:
        // If it has a ShadowRoot, ignore all child elements - these will be picked
        // up by the <content> or <shadow> elements. Descend straight into the
        // ShadowRoot.
        var shadowRoot = /** @type {!HTMLElement} */element.shadowRoot;
        if (shadowRoot) {
          composedTreeWalk(shadowRoot, callback);
          return;
        }
  
        // If it is a <content> element, descend into distributed elements - these
        // are elements from outside the shadow root which are rendered inside the
        // shadow DOM.
        if (element.localName == 'content') {
          var content = /** @type {!HTMLContentElement} */element;
          // Verifies if ShadowDom v0 is supported.
          var distributedNodes = content.getDistributedNodes ? content.getDistributedNodes() : [];
          for (var i = 0; i < distributedNodes.length; i++) {
            composedTreeWalk(distributedNodes[i], callback);
          }
          return;
        }
  
        // If it is a <slot> element, descend into assigned nodes - these
        // are elements from outside the shadow root which are rendered inside the
        // shadow DOM.
        if (element.localName == 'slot') {
          var slot = /** @type {!HTMLSlotElement} */element;
          // Verify if ShadowDom v1 is supported.
          var _distributedNodes = slot.assignedNodes ? slot.assignedNodes({ flatten: true }) : [];
          for (var _i = 0; _i < _distributedNodes.length; _i++) {
            composedTreeWalk(_distributedNodes[_i], callback);
          }
          return;
        }
      }
  
      // If it is neither the parent of a ShadowRoot, a <content> element, a <slot>
      // element, nor a <shadow> element recurse normally.
      var child = node.firstChild;
      while (child != null) {
        composedTreeWalk(child, callback);
        child = child.nextSibling;
      }
    }
  
    /**
     * Adds a style element to the node containing the inert specific styles
     * @param {!Node} node
     */
    function addInertStyle(node) {
      if (node.querySelector('style#inert-style, link#inert-style')) {
        return;
      }
      var style = document.createElement('style');
      style.setAttribute('id', 'inert-style');
      style.textContent = '\n' + '[inert] {\n' + '  pointer-events: none;\n' + '  cursor: default;\n' + '}\n' + '\n' + '[inert], [inert] * {\n' + '  -webkit-user-select: none;\n' + '  -moz-user-select: none;\n' + '  -ms-user-select: none;\n' + '  user-select: none;\n' + '}\n';
      node.appendChild(style);
    }
  
    if (!Element.prototype.hasOwnProperty('inert')) {
      /** @type {!InertManager} */
      var inertManager = new InertManager(document);
  
      Object.defineProperty(Element.prototype, 'inert', {
        enumerable: true,
        /** @this {!Element} */
        get: function get() {
          return this.hasAttribute('inert');
        },
        /** @this {!Element} */
        set: function set(inert) {
          inertManager.setInert(this, inert);
        }
      });
    }
  })();
  