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

Source/web/WebDevToolsAgentImpl.cpp

Index: Source/web/WebDevToolsAgentImpl.cpp
diff --git a/Source/web/WebDevToolsAgentImpl.cpp b/Source/web/WebDevToolsAgentImpl.cpp
index 3de41ae36c75dba5c172bf59b1ac90751058f43c..82119e49ef577bfd49c3b0747b5a5f6a72c4426b 100644
--- a/Source/web/WebDevToolsAgentImpl.cpp
+++ b/Source/web/WebDevToolsAgentImpl.cpp
@@ -163,6 +163,17 @@ private:
         // 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;