DevTools: Fix an exception on adding watch expression.

third_party/WebKit/Source/devtools/front_end/components/ObjectPropertiesSection.js

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  * Copyright (C) 2009 Joseph Pecoraro
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 817 matching lines @@
 
     // Lie about our children to prevent expanding on double click and to collapse subproperties.
     this.setExpandable(false);
     this.listItemElement.classList.add('editing-sub-part');
     this.valueElement.classList.add('hidden');
 
     this._prompt = new Components.ObjectPropertyPrompt();
 
     var proxyElement =
         this._prompt.attachAndStartEditing(this._editableDiv, this._editingCommitted.bind(this, originalContent));
-    this.listItemElement.getComponentSelection().setBaseAndExtent(this._editableDiv, 0, this._editableDiv, 1);
+    this.listItemElement.getComponentSelection().selectAllChildren(this._editableDiv);
     proxyElement.addEventListener('keydown', this._promptKeyDown.bind(this, originalContent), false);
   }
 
   _editingEnded() {
     this._prompt.detach();
     delete this._prompt;
     this._editableDiv.remove();
     this._updateExpandable();
     this.listItemElement.scrollLeft = 0;
     this.listItemElement.classList.remove('editing-sub-part');
@@ skipping 496 matching lines @@
     }
     var treeOutlineId = treeElement.treeOutline[Components.ObjectPropertiesSectionExpandController._treeOutlineId];
     result = treeOutlineId + (result ? ':' + result : '');
     treeElement[Components.ObjectPropertiesSectionExpandController._cachedPathSymbol] = result;
     return result;
   }
 };
 
 Components.ObjectPropertiesSectionExpandController._cachedPathSymbol = Symbol('cachedPath');
 Components.ObjectPropertiesSectionExpandController._treeOutlineId = Symbol('treeOutlineId');