service worker: More OnceCallback migration in ServiceWorkerContext.

Also do other cleanups in comments, etc.

Bug: 755477
TBR: lazyboy@ (extensions), markusheintz@  (browsing_data) [trivial changes]
Change-Id: Ib0a7ae68497a9b10970f582522a359b4611f11ff
Reviewed-on: https://chromium-review.googlesource.com/652729
Reviewed-by: Matt Falkenhagen <[email protected]>
Reviewed-by: Istiaque Ahmed <[email protected]>
Reviewed-by: Kinuko Yasuda <[email protected]>
Commit-Queue: Matt Falkenhagen <[email protected]>
Cr-Commit-Position: refs/heads/master@{#500247}
diff --git a/chrome/browser/extensions/service_worker_apitest.cc b/chrome/browser/extensions/service_worker_apitest.cc
index ed2ed74..bbb364d 100644
--- a/chrome/browser/extensions/service_worker_apitest.cc
+++ b/chrome/browser/extensions/service_worker_apitest.cc
@@ -189,7 +189,7 @@
       run_loop->Quit();
     };
     sw_context->CountExternalRequestsForTest(
-        origin, base::Bind(set_ref_count, &ref_count, &run_loop));
+        origin, base::BindOnce(set_ref_count, &ref_count, &run_loop));
     run_loop.Run();
     return ref_count;
   }