DevTools: support cross-navigation instrumentation.

webkit/api/public/WebDevToolsAgentClient.h

 /*
  * Copyright (C) 2009 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 32 matching lines @@
                                        const WebString& param1,
                                        const WebString& param2,
                                        const WebString& param3) = 0;
 
     // Invalidates widget which leads to the repaint.
     virtual void forceRepaint() = 0;
 
     // Returns the identifier of the entity hosting this agent.
     virtual int hostIdentifier() = 0;
 
+    // Notifies host upon runtime feature being enabled/disabled.
+    virtual void runtimeFeatureStateChanged(const WebString& feature, bool enabled) = 0;
+
 protected:
     ~WebDevToolsAgentClient() {}
 };
 
 } // namespace WebKit
 
 #endif