Move "oauth2" manifest key parsing out of Extension class.

chrome/common/extensions/manifest_handler.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 CHROME_COMMON_EXTENSIONS_MANIFEST_HANDLER_H_
 #define CHROME_COMMON_EXTENSIONS_MANIFEST_HANDLER_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 12 matching lines @@
   ManifestHandler();
   virtual ~ManifestHandler();
 
   // Attempts to parse the manifest value.
   // Returns true on success or false on failure; if false, |error| will
   // be set to a failure message.
   virtual bool Parse(const base::Value* value,
                      Extension* extension,
                      string16* error) = 0;
 
+  // Perform any initialization which is necessary when the Handler's key is
+  // not present in the manifest.
+  // Returns true on success or false on failure; if false, |error| will
+  // be set to a failure message.
+  virtual bool HasNoKey(Extension* extension, string16* error);
+
   // Associate |handler| with |key| in the manifest. Takes ownership
   // of |handler|. TODO(yoz): Decide how to handle dotted subkeys.
   // WARNING: Manifest handlers registered only in the browser process
   // are not available to renderers.
   static void Register(const std::string& key, ManifestHandler* handler);
 
   // Get the manifest handler associated with |key|, or NULL
   // if there is none.
   static ManifestHandler* Get(const std::string& key);
 
   // If the handler is not handling most of the keys, it may be
   // more efficient to have a list of keys to iterate over.
   // TODO(yoz): this isn't the long-term solution.
   static std::vector<std::string> GetKeys();
 };
 
 
 }  // namespace extensions
 
 #endif  // CHROME_COMMON_EXTENSIONS_MANIFEST_HANDLER_H_