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

chrome/browser/chromeos/gdata/gdata_file_system_unittest.cc

 // 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.
 
 #include <string>
 #include <vector>
 
 #include "base/bind.h"
 #include "base/file_path.h"
 #include "base/file_util.h"
@@ skipping 220 matching lines @@
     mock_free_disk_space_checker_ = new StrictMock<MockFreeDiskSpaceGetter>;
     SetFreeDiskSpaceGetterForTesting(mock_free_disk_space_checker_);
 
     scoped_refptr<base::SequencedWorkerPool> pool =
         content::BrowserThread::GetBlockingPool();
     blocking_task_runner_ =
         pool->GetSequencedTaskRunner(pool->GetSequenceToken());
 
     cache_ = GDataCache::CreateGDataCacheOnUIThread(
         GDataCache::GetCacheRootPath(profile_.get()), blocking_task_runner_);
+    cache_->ForceMetadataMapForTesting();
 
     mock_uploader_.reset(new StrictMock<MockGDataUploader>);
     mock_webapps_registry_.reset(new StrictMock<MockDriveWebAppsRegistry>);
 
     ASSERT_FALSE(file_system_);
     file_system_ = new GDataFileSystem(profile_.get(),
                                        cache_,
                                        mock_doc_service_,
                                        mock_uploader_.get(),
                                        mock_webapps_registry_.get(),
@@ skipping 2367 matching lines @@
 
   // Try to close the same file twice.
   file_system_->CloseFile(kFileInRoot, close_file_callback);
   message_loop_.Run();
 
   // It must fail.
   EXPECT_EQ(GDATA_FILE_ERROR_NOT_FOUND, callback_helper_->last_error_);
 }
 
 }   // namespace gdata