DevTools: defer styles delta calculation to until the end of the task.

Source/core/inspector/InspectorBaseAgent.h

 /*
  * Copyright (C) 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 37 matching lines @@
     explicit InspectorAgent(const String&);
     virtual ~InspectorAgent();
 
     virtual void init() { }
     virtual void setFrontend(InspectorFrontend*) { }
     virtual void clearFrontend() { }
     virtual void restore() { }
     virtual void registerInDispatcher(InspectorBackendDispatcher*) = 0;
     virtual void discardAgent() { }
     virtual void didCommitLoadForMainFrame() { }
+    virtual void flushPendingFrontendMessages() { }
 
     String name() { return m_name; }
     void appended(InstrumentingAgents*, InspectorState*);
 
 protected:
     InstrumentingAgents* m_instrumentingAgents;
     InspectorState* m_state;
 
 private:
     String m_name;
 };
 
 class InspectorAgentRegistry {
 public:
     InspectorAgentRegistry(InstrumentingAgents*, InspectorCompositeState*);
     void append(PassOwnPtr<InspectorAgent>);
 
     void setFrontend(InspectorFrontend*);
     void clearFrontend();
     void restore();
     void registerInDispatcher(InspectorBackendDispatcher*);
     void discardAgents();
+    void flushPendingFrontendMessages();
 
 private:
     InstrumentingAgents* m_instrumentingAgents;
     InspectorCompositeState* m_inspectorState;
     Vector<OwnPtr<InspectorAgent> > m_agents;
 };
 
 template<typename T>
 class InspectorBaseAgent : public InspectorAgent {
 public:
     virtual ~InspectorBaseAgent() { }
 
     virtual void registerInDispatcher(InspectorBackendDispatcher* dispatcher) OVERRIDE FINAL
     {
         dispatcher->registerAgent(static_cast<T*>(this));
     }
 
 protected:
     InspectorBaseAgent(const String& name) : InspectorAgent(name)
     {
     }
 };
 
 } // namespace WebCore
 
 #endif // !defined(InspectorBaseAgent_h)