[DevTools] Fix a crash in site-per-process tests.

Source/web/WebDevToolsAgentImpl.cpp

 /*
  * Copyright (C) 2010-2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 262 matching lines @@
     }
 
 private:
     OwnPtr<WebDevToolsAgent::MessageDescriptor> m_descriptor;
 };
 
 // static
 PassOwnPtrWillBeRawPtr<WebDevToolsAgentImpl> WebDevToolsAgentImpl::create(WebLocalFrameImpl* frame, WebDevToolsAgentClient* client)
 {
     WebViewImpl* view = frame->viewImpl();
-    bool isMainFrame = view && view->mainFrameImpl() == frame;
+    // TODO(dgozman): sometimes view->mainFrameImpl() does return null, even though |frame| is meant to be main frame.
+    // See http://crbug.com/526162.
+    bool isMainFrame = view && !frame->parent();
     if (!isMainFrame) {
         WebDevToolsAgentImpl* agent = new WebDevToolsAgentImpl(frame, client, InspectorOverlayImpl::createEmpty());
         if (frame->frameWidget())
             agent->layerTreeViewChanged(toWebFrameWidgetImpl(frame->frameWidget())->layerTreeView());
         return adoptPtrWillBeNoop(agent);
     }
 
     WebDevToolsAgentImpl* agent = new WebDevToolsAgentImpl(frame, client, InspectorOverlayImpl::create(view));
     agent->registerAgent(InspectorRenderingAgent::create(view));
     agent->registerAgent(InspectorEmulationAgent::create(view));
@@ skipping 461 matching lines @@
     if (!InspectorBackendDispatcher::getCommandName(message, &commandName))
         return false;
     return commandName == InspectorBackendDispatcher::commandName(InspectorBackendDispatcher::kDebugger_pauseCmd)
         || commandName == InspectorBackendDispatcher::commandName(InspectorBackendDispatcher::kDebugger_setBreakpointCmd)
         || commandName == InspectorBackendDispatcher::commandName(InspectorBackendDispatcher::kDebugger_setBreakpointByUrlCmd)
         || commandName == InspectorBackendDispatcher::commandName(InspectorBackendDispatcher::kDebugger_removeBreakpointCmd)
         || commandName == InspectorBackendDispatcher::commandName(InspectorBackendDispatcher::kDebugger_setBreakpointsActiveCmd);
 }
 
 } // namespace blink