Fixes Dartium crashing if trying to debug code associated with an iFrame.

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 145 matching lines @@
 
     void run(LocalFrame* frame) override
     {
         if (m_running)
             return;
         m_running = true;
 
         // 0. Flush pending frontend messages.
         WebLocalFrameImpl* frameImpl = WebLocalFrameImpl::fromFrame(frame);
         WebDevToolsAgentImpl* agent = frameImpl->devToolsAgentImpl();
+
+        // FIXME(terry): Dart fix if the current iFrame doesn't have a dev tools
+        //               agent then use the main frame's agent.  This allow's
+        //               debugging Dart code associated with an iFrame (that's
+        //               not the main frame).
+        if (!agent) {
+          LocalFrame* mainFrame = frameImpl->frame()->localFrameRoot();
+          frameImpl = WebLocalFrameImpl::fromFrame(mainFrame);
+          agent = frameImpl->devToolsAgentImpl();
+        }
+
         agent->flushPendingProtocolNotifications();
 
         Vector<WebViewImpl*> views;
         Vector<WebFrameWidgetImpl*> widgets;
 
         // 1. Disable input events.
         const HashSet<WebViewImpl*>& viewImpls = WebViewImpl::allInstances();
         HashSet<WebViewImpl*>::const_iterator viewImplsEnd = viewImpls.end();
         for (HashSet<WebViewImpl*>::const_iterator it =  viewImpls.begin(); it != viewImplsEnd; ++it) {
             WebViewImpl* view = *it;
@@ skipping 582 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