[Extensions] Update ExtensionService references in c/b/media_galleries

Update references to ExtensionService in c/b/media_galleries to use
extensions::ExtensionService.

There should be no behavior change as a result of this CL.

Bug: 117261
Change-Id: I4a097c316ead2833466274cca7c2c36e8ef0c8c0
Reviewed-on: https://chromium-review.googlesource.com/1080043Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#563091}

chrome/browser/media_galleries/fileapi/media_file_system_backend.cc

@@ -91,7 +91,7 @@ void AttemptAutoMountOnUIThread(
     Profile* profile =
         Profile::FromBrowserContext(web_contents->GetBrowserContext());
 
-    ExtensionService* extension_service =
+    extensions::ExtensionService* extension_service =
         extensions::ExtensionSystem::Get(profile)->extension_service();
     const extensions::Extension* extension =
         extension_service->GetExtensionById(storage_domain,

chrome/browser/media_galleries/media_galleries_test_util.cc

@@ -79,7 +79,7 @@ scoped_refptr<extensions::Extension> AddMediaGalleriesApp(
       extensions::Extension::ENABLED,
       syncer::StringOrdinal::CreateInitialOrdinal(),
       std::string());
-  ExtensionService* extension_service =
+  extensions::ExtensionService* extension_service =
       extensions::ExtensionSystem::Get(profile)->extension_service();
   extension_service->AddExtension(extension.get());
   extension_service->EnableExtension(extension->id());