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

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

Clean up a few other instances when the extensions:: prefix is
unnecessary.

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

Bug: 117261
Change-Id: I95616145a995bdf5828036b682647d6e61649c8c
Reviewed-on: https://chromium-review.googlesource.com/1076974
Reviewed-by: Istiaque Ahmed <[email protected]>
Commit-Queue: Devlin <[email protected]>
Cr-Commit-Position: refs/heads/master@{#562678}
diff --git a/chrome/browser/extensions/chrome_app_api_browsertest.cc b/chrome/browser/extensions/chrome_app_api_browsertest.cc
index fc02b55..db24543b 100644
--- a/chrome/browser/extensions/chrome_app_api_browsertest.cc
+++ b/chrome/browser/extensions/chrome_app_api_browsertest.cc
@@ -199,8 +199,9 @@
   EXPECT_TRUE(IsAppInstalledInMainFrame());
 
   // Disable the extension and verify the state.
-  ExtensionService* service = extensions::ExtensionSystem::Get(
-      browser()->profile())->extension_service();
+  extensions::ExtensionService* service =
+      extensions::ExtensionSystem::Get(browser()->profile())
+          ->extension_service();
   service->DisableExtension(
       extension->id(),
       extensions::disable_reason::DISABLE_PERMISSIONS_INCREASE);