Implement initialization for GDataCache to use in-memory metadata for tests.

chrome/browser/chromeos/gdata/gdata_cache.h

Index: chrome/browser/chromeos/gdata/gdata_cache.h
diff --git a/chrome/browser/chromeos/gdata/gdata_cache.h b/chrome/browser/chromeos/gdata/gdata_cache.h
index c9eb8d449ae7550f6c7c71d32de2868a053ba45a..2c67f0ea21e9ee98e7677bbf3f9ea482d3622541 100644
--- a/chrome/browser/chromeos/gdata/gdata_cache.h
+++ b/chrome/browser/chromeos/gdata/gdata_cache.h
@@ -272,6 +272,9 @@ class GDataCache {
   // Utility method to call Initialize on UI thread.
   void RequestInitializeOnUIThread();
 
+  // Utility method to call InitializeForTesting on UI thread.
+  void RequestInitializeOnUIThreadForTesting();
+
   // Force a rescan of cache files, for testing.
   void ForceRescanOnUIThreadForTesting();
 
@@ -329,6 +332,10 @@ class GDataCache {
   // Initializes the cache.
   void Initialize();
 
+  // Initializes the cache with in-memory cache for testing.
+  // The in-memory cache is used since it's faster than the db.
+  void InitializeForTesting();
+
   // Deletes the cache.
   void Destroy();