[DevTools] Fix frontend host race and assert.

content/renderer/devtools/devtools_client.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_RENDERER_DEVTOOLS_DEVTOOLS_CLIENT_H_
 #define CONTENT_RENDERER_DEVTOOLS_DEVTOOLS_CLIENT_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 27 matching lines @@
   void DidClearWindowObject() override;
 
   // WebDevToolsFrontendClient implementation.
   void sendMessageToEmbedder(const blink::WebString&) override;
 
   bool isUnderTest() override;
 
   void OnDispatchOnInspectorFrontend(const std::string& message,
                                      uint32 total_size);
 
+  std::string compatibility_script_;
   scoped_ptr<blink::WebDevToolsFrontend> web_tools_frontend_;
-  std::string compatibility_script_;
 
   DISALLOW_COPY_AND_ASSIGN(DevToolsClient);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_DEVTOOLS_DEVTOOLS_CLIENT_H_