drive: Add the local largest changestamp to chrome:drive-internals

chrome/browser/chromeos/drive/drive_file_system.h

Index: chrome/browser/chromeos/drive/drive_file_system.h
diff --git a/chrome/browser/chromeos/drive/drive_file_system.h b/chrome/browser/chromeos/drive/drive_file_system.h
index 60eb78dcbc64a385ccae2c48d37f892f31e005cf..18cfc7f00db05e70e1205fbaf9f3ec32bf2f0c69 100644
--- a/chrome/browser/chromeos/drive/drive_file_system.h
+++ b/chrome/browser/chromeos/drive/drive_file_system.h
@@ -138,6 +138,7 @@ class DriveFileSystem : public DriveFileSystemInterface,
                                scoped_ptr<gdata::DocumentEntry> entry,
                                const FilePath& file_content_path,
                                const base::Closure& callback) OVERRIDE;
+  virtual DriveFileSystemMetadata GetMetadata() const OVERRIDE;
 
   // content::NotificationObserver implementation.
   virtual void Observe(int type,
@@ -154,8 +155,6 @@ class DriveFileSystem : public DriveFileSystemInterface,
   virtual void OnDocumentFeedFetched(int num_accumulated_entries) OVERRIDE;
   virtual void OnFeedFromServerLoaded() OVERRIDE;
 
-  DriveResourceMetadata* ResourceMetadata() { return resource_metadata_.get(); }
-
   // Used in tests to load the root feed from the cache.
   void LoadRootFeedFromCacheForTesting();