[Sync] Rip out overly-complicated ExtensionData class

chrome/browser/extensions/extension_sync_data.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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_EXTENSION_SYNC_DATA_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_SYNC_DATA_H_
 #pragma once
 
 #include <string>
 
 #include "base/version.h"
 #include "googleurl/src/gurl.h"
 
 // A struct that encapsulates the synced properties of an Extension.
 struct ExtensionSyncData {
   ExtensionSyncData();
   ~ExtensionSyncData();
 
+  // Merge |new_data| into this object.  All version-independent
+  // properties are copied from |new_data|, and version-dependent
+  // properties are copied only if |new_data|'s version is equal to or
+  // greater than the current version.
+  void Merge(const ExtensionSyncData& new_data);
+
   std::string id;
 
   // Version-independent properties (i.e., used even when the
   // version of the currently-installed extension doesn't match
   // |version|).
   bool uninstalled;
   bool enabled;
   bool incognito_enabled;
 
   // Version-dependent properties (i.e., should be used only when the
   // version of the currenty-installed extension matches |version|).
   Version version;
   GURL update_url;
-
   // Used only for debugging.
   std::string name;
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_SYNC_DATA_H_