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

chrome/browser/chromeos/gdata/gdata_cache_metadata.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_BROWSER_CHROMEOS_GDATA_GDATA_CACHE_METADATA_H_
 #define CHROME_BROWSER_CHROMEOS_GDATA_GDATA_CACHE_METADATA_H_
 
 #include <map>
 #include <vector>
 #include <string>
@@ skipping 13 matching lines @@
   // Callback for Iterate().
   typedef base::Callback<void(const std::string& resource_id,
                               const GDataCacheEntry& cache_entry)>
       IterateCallback;
 
   // A map table of cache file's resource id to its CacheEntry* entry.
   typedef std::map<std::string, GDataCacheEntry> CacheMap;
 
   virtual ~GDataCacheMetadata();
 
-  // |pool| and |sequence_token| are used to assert that the functions are
-  // called on the right sequenced worker pool with the right sequence token.
-  //
-  // For testing, the thread assertion can be disabled by passing NULL and
-  // the default value of SequenceToken.
+  // Creates GDataCacheMetadata instance.
   static scoped_ptr<GDataCacheMetadata> CreateGDataCacheMetadata(
       base::SequencedTaskRunner* blocking_task_runner);
 
+  // Creates GDataCacheMetadata instance. This uses FakeGDataCacheMetadata,
+  // which is an in-memory implmentation and faster than GDataCacheMetadataDB.
+  static scoped_ptr<GDataCacheMetadata> CreateGDataCacheMetadataForTesting(
+      base::SequencedTaskRunner* blocking_task_runner);
+
   // Initialize the cache metadata store.
   virtual void Initialize(const std::vector<FilePath>& cache_paths) = 0;
   // Adds a new cache entry corresponding to |resource_id| if it doesn't
   // exist, otherwise update the existing entry.
   virtual void AddOrUpdateCacheEntry(const std::string& resource_id,
                                      const GDataCacheEntry& cache_entry) = 0;
 
   // Removes entry corresponding to |resource_id| from cache map.
   virtual void RemoveCacheEntry(const std::string& resource_id) = 0;
 
@@ skipping 26 matching lines @@
 
  private:
   scoped_refptr<base::SequencedTaskRunner> blocking_task_runner_;
 
   DISALLOW_COPY_AND_ASSIGN(GDataCacheMetadata);
 };
 
 }  // namespace gdata
 
 #endif  // CHROME_BROWSER_CHROMEOS_GDATA_GDATA_CACHE_METADATA_H_