switch mediaGalleries to .idl api definition

chrome/browser/extensions/api/media_galleries/media_galleries_apitest.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 "base/command_line.h"
 #include "chrome/browser/extensions/extension_apitest.h"
 #include "chrome/common/chrome_switches.h"
 
 namespace {
 
 class ExperimentalExtensionApiTest : public ExtensionApiTest {
  public:
   virtual void SetUpCommandLine(CommandLine* command_line) OVERRIDE {
     ExtensionApiTest::SetUpCommandLine(command_line);
     command_line->AppendSwitch(switches::kEnableExperimentalExtensionApis);
   }
 };
 
 }  // namespace
 
 IN_PROC_BROWSER_TEST_F(ExperimentalExtensionApiTest, MediaGallery) {
-  ASSERT_TRUE(RunExtensionTest("media_gallery")) << message_;
+  ASSERT_TRUE(RunExtensionTest("media_galleries")) << message_;
 }