message: clearer naming in ScrollPanel
diff: @@ -601,16 +601,17 @@ module.exports = React.createClass({
  }
  const scrollNode = this._getScrollNode();
  - const scrollBottom = scrollNode.scrollTop + scrollNode.clientHeight;
  -
  + const scrollTop = scrollNode.scrollTop;
  + const viewportBottom = scrollTop + scrollNode.clientHeight;
  const nodeBottom = node.offsetTop + node.clientHeight;
  - const scrollDelta = nodeBottom + pixelOffset - scrollBottom;
  + const intendedViewportBottom = nodeBottom + pixelOffset;
  + const scrollDelta = intendedViewportBottom - viewportBottom;
  debuglog("ScrollPanel: scrolling to token '" + scrollToken + "'+" +
  pixelOffset + " (delta: "+scrollDelta+")");
  - if (scrollDelta != 0) {
  - this._setScrollTop(scrollNode.scrollTop + scrollDelta);
  + if (scrollDelta !== 0) {
  + this._setScrollTop(scrollTop + scrollDelta);
  }
  },
  @@ -622,7 +623,7 @@ module.exports = React.createClass({
  }
  const scrollNode = this._getScrollNode();
  - const scrollBottom = scrollNode.scrollTop + scrollNode.clientHeight;
  + const viewportBottom = scrollNode.scrollTop + scrollNode.clientHeight;
  const itemlist = this.refs.itemlist;
  const messages = itemlist.children;
  @@ -636,7 +637,7 @@ module.exports = React.createClass({
  node = messages[i];
  // break at the first message (coming from the bottom)
  // that has it's offsetTop above the bottom of the viewport.
  - if (node.offsetTop < scrollBottom) {
  + if (node.offsetTop < viewportBottom) {
  // Use this node as the scrollToken
  break;
  }
  @@ -652,7 +653,7 @@ module.exports = React.createClass({
  this.scrollState = {
  stuckAtBottom: false,
  trackedScrollToken: node.dataset.scrollTokens.split(',')[0],
  - pixelOffset: scrollBottom - nodeBottom,
  + pixelOffset: viewportBottom - nodeBottom,
  };
  },
  