drive: Return cancel closure from FileSystem::GetFileContent

chrome/browser/chromeos/drive/dummy_file_system.cc

Index: chrome/browser/chromeos/drive/dummy_file_system.cc
diff --git a/chrome/browser/chromeos/drive/dummy_file_system.cc b/chrome/browser/chromeos/drive/dummy_file_system.cc
new file mode 100644
index 0000000000000000000000000000000000000000..696d695bf42682cf66382237dbe672195938483a
--- /dev/null
+++ b/chrome/browser/chromeos/drive/dummy_file_system.cc
@@ -0,0 +1,17 @@
+// Copyright 2014 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 "chrome/browser/chromeos/drive/dummy_file_system.h"
+
+namespace drive {
+
+base::Closure DummyFileSystem::GetFileContent(
+      const base::FilePath& file_path,
+      const GetFileContentInitializedCallback& initialized_callback,
+      const google_apis::GetContentCallback& get_content_callback,
+      const FileOperationCallback& completion_callback) {
+  return base::Bind(&base::DoNothing);
+}
+
+}  // namespace drive