message: prevent height doubling when resizing
  caused by mixing up absolute height with incremental height
diff: @@ -71,7 +71,7 @@ export class Layout {
  openHandle(id) {
  const index = this._getSectionIndex(id);
  //log(`openHandle resolved ${id} to ${index}`);
  - return new Handle(this, index);
  + return new Handle(this, index, this._originalHeights[index]);
  }
  _getAvailableHeight() {
  @@ -258,13 +258,14 @@ export class Layout {
  }
  class Handle {
  - constructor(layout, anchor) {
  + constructor(layout, anchor, height) {
  this._layout = layout;
  this._anchor = anchor;
  + this._initialHeight = height;
  }
  - setOffset(offset) {
  - this._layout._relayout(this._anchor, offset);
  + setHeight(height) {
  + this._layout._relayout(this._anchor, height - this._initialHeight);
  }
  finish() {
  @@ -283,7 +284,7 @@ export class Distributor extends FixedDistributor {
  this._handle.finish();
  }
  - resize(offset) {
  - this._handle.setOffset(offset);
  + resize(height) {
  + this._handle.setHeight(height);
  }
  }
  