Move the "extension" namespace from extension_api.json into extension_api_extension.json.

chrome/browser/extensions/extension_clear_api.h

 // Copyright (c) 2011 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 Clear API functions, which entail
 // clearing browsing data, and clearing the browser's cache (which, let's be
-// honest, are the same thing), as specified in
-// chrome/common/extensions/api/extension_api.json.
+// honest, are the same thing), as specified in the extension API JSON.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_EXTENSION_CLEAR_API_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_CLEAR_API_H_
 #pragma once
 
 #include <string>
 
 #include "chrome/browser/browsing_data_remover.h"
 #include "chrome/browser/extensions/extension_function.h"
 
@@ skipping 110 matching lines @@
   virtual ~ClearPasswordsFunction() {}
 
  protected:
   // BrowsingDataTypeExtensionFunction interface method.
   virtual int GetRemovalMask() const OVERRIDE;
 
   DECLARE_EXTENSION_FUNCTION_NAME("experimental.clear.passwords")
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_CLEAR_API_H_