Avoid using declarations in headers which introduce symbol conflicts.

third_party/WebKit/Source/modules/storage/InspectorDOMStorageAgent.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) 2013 Samsung Electronics. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 26 matching lines @@
 #include "core/frame/LocalFrame.h"
 #include "core/inspector/InspectedFrames.h"
 #include "core/page/Page.h"
 #include "modules/storage/Storage.h"
 #include "modules/storage/StorageNamespace.h"
 #include "modules/storage/StorageNamespaceController.h"
 #include "platform/weborigin/SecurityOrigin.h"
 
 namespace blink {
 
+using protocol::Response;
+
 namespace DOMStorageAgentState {
 static const char domStorageAgentEnabled[] = "domStorageAgentEnabled";
 };
 
 static Response toResponse(ExceptionState& exceptionState) {
   if (!exceptionState.hadException())
     return Response::OK();
   return Response::Error(DOMException::getErrorName(exceptionState.code()) +
                          " " + exceptionState.message());
 }
@@ skipping 167 matching lines @@
   StorageNamespace* sessionStorage =
       StorageNamespaceController::from(m_page)->sessionStorage();
   if (!sessionStorage)
     return Response::Error("SessionStorage is not supported");
   storageArea =
       sessionStorage->storageArea(frame->document()->getSecurityOrigin());
   return Response::OK();
 }
 
 }  // namespace blink