[DevTools] Make resource tree model optional

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

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @constructor
  * @implements {WebInspector.TargetManager.Observer}
  * @param {!WebInspector.TargetManager} targetManager
  * @param {!WebInspector.Context} context
  */
@@ skipping 112 matching lines @@
             return true;
         if (!this._lastSelectedContextId && this._isMainFrameContext(executionContext))
             return true;
         return false;
     },
 
     /**
      * @param {!WebInspector.ExecutionContext} executionContext
      * @return {boolean}
      */
     _isMainFrameContext: function(executionContext)

[pfeldman, 2016/07/07 17:44:14]

The name is misleading - we want to know whether this is a default context,
should be

_isDefault() and should check for belonging to the main target.

[eostroukhov-old, 2016/07/13 23:30:58]

Done. Note that the main target check is by checking if there's a parent target.
It is to make sure tests work - discussed it with +dgozman, 

     {
-        if (!executionContext.isDefault)
+        if (!executionContext.isDefault || !executionContext.frameId)
             return false;
-        var frame = executionContext.target().resourceTreeModel.frameForId(executionContext.frameId);
+        var resourceTreeModel = WebInspector.ResourceTreeModel.fromTarget(executionContext.target());
+        if (!resourceTreeModel)
+            return false;
+        var frame = resourceTreeModel.frameForId(executionContext.frameId);
         if (frame && frame.isMainFrame())
             return true;
         return false;
     },
 
     /**
      * @param {!WebInspector.Event} event
      */
     _onExecutionContextCreated: function(event)
     {
@@ skipping 66 matching lines @@
     var expressionString = expressionRange.toString();
 
     // The "[" is also a stop character, except when it's the last character of the expression.
     var pos = expressionString.lastIndexOf("[", expressionString.length - 2);
     if (pos !== -1)
         expressionString = expressionString.substr(pos + 1);
 
     var prefix = wordRange.toString();
     executionContext.completionsForExpression(expressionString, text, cursorOffset, prefix, force, completionsReadyCallback);
 }