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

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

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

Bug: 117261
Change-Id: Ie3133eeb0a9778c909420b3f531e2d34d4270686
Reviewed-on: https://chromium-review.googlesource.com/1079901Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#563044}

chrome/browser/notifications/chrome_ash_message_center_client_unittest.cc

@@ -110,7 +110,7 @@ TEST_F(ChromeAshMessageCenterClientTest, NotifierSortOrder) {
       static_cast<extensions::TestExtensionSystem*>(
           extensions::ExtensionSystem::Get(profile));
   base::CommandLine command_line(base::CommandLine::NO_PROGRAM);
-  ExtensionService* extension_service =
+  extensions::ExtensionService* extension_service =
       test_extension_system->CreateExtensionService(
           &command_line, base::FilePath() /* install_directory */,
           false /* autoupdate_enabled*/);

chrome/browser/notifications/platform_notification_service_unittest.cc

@@ -288,7 +288,7 @@ TEST_F(PlatformNotificationServiceTest, ExtensionPermissionChecks) {
       static_cast<extensions::TestExtensionSystem*>(
           extensions::ExtensionSystem::Get(profile_));
 
-  ExtensionService* extension_service =
+  extensions::ExtensionService* extension_service =
       test_extension_system->CreateExtensionService(
           &command_line, base::FilePath() /* install_directory */,
           false /* autoupdate_enabled */);