DevTools: provide the debugger detach reason in chrome.debugger.onDetach extension API.

chrome/browser/extensions/api/debugger/debugger_api.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.
 
 // Defines the Chrome Extensions Debugger API functions for attaching debugger
 // to the page.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_API_DEBUGGER_DEBUGGER_API_H_
 #define CHROME_BROWSER_EXTENSIONS_API_DEBUGGER_DEBUGGER_API_H_
 
 #include <string>
 
 #include "chrome/browser/extensions/extension_function.h"
 
 // Base debugger function.
 
 class ExtensionDevToolsClientHost;
 
 namespace base {
 class DictionaryValue;
 }
 
 namespace content {
+class DevToolsClientHost;
 class WebContents;
 }
 
 class DebuggerFunction : public AsyncExtensionFunction {
  protected:
   DebuggerFunction();
   virtual ~DebuggerFunction() {}
 
   bool InitTabContents();
   bool InitClientHost();
@@ skipping 39 matching lines @@
   SendCommandDebuggerFunction();
   void SendResponseBody(base::DictionaryValue* result);
 
  protected:
   virtual ~SendCommandDebuggerFunction();
 
   // ExtensionFunction:
   virtual bool RunImpl() OVERRIDE;
 };
 
+class DebuggerApi {
+ public:
+  // Marks ExtensionDevToolsClientHost as replaced with the bundled devtools
+  // so that we could report proper disconnect reason.
+  static void MarkDevToolsClientHostAsReplaced(
+      content::DevToolsClientHost* client_host);
+};
+
 #endif  // CHROME_BROWSER_EXTENSIONS_API_DEBUGGER_DEBUGGER_API_H_