ServiceWorker: Make skipWaiting only works on documents using current registration

content/browser/service_worker/service_worker_provider_host.cc

Index: content/browser/service_worker/service_worker_provider_host.cc
diff --git a/content/browser/service_worker/service_worker_provider_host.cc b/content/browser/service_worker/service_worker_provider_host.cc
index 2bb6499487916db409c6eecbd9c10cae0863b7e2..97d37cedb21b5b31b49f8456ac4c5202831bae57 100644
--- a/content/browser/service_worker/service_worker_provider_host.cc
+++ b/content/browser/service_worker/service_worker_provider_host.cc
@@ -84,6 +84,8 @@ void ServiceWorkerProviderHost::OnRegistrationFailed(
 void ServiceWorkerProviderHost::OnSkippedWaiting(
     ServiceWorkerRegistration* registration) {
   DCHECK_EQ(associated_registration_.get(), registration);
+  if (!controlling_version_)

[falken, 2014/12/15 02:29:25]

I think some explanation here using comments or function names would be good.
The key points are:
1. A client is using a registration if it is controlled by the active worker of
the registration (definition).
2. skippedWaiting alters a registration but does not cause a client to start
using the registration.

Maybe a helper function like ServiceWorkerProviderHost::IsUsingRegistration()
along with a comment?

[xiang, 2014/12/15 06:00:52]

I added these comments. I think a IsUsingRegistration() method maybe not proper
here as it is in a transition state, the controlling_version_ is not equal to
registration->active_version().

[falken, 2014/12/15 06:18:01]

My imagination was something like { return
associated_registration_->active_version() == controlling_version_; }

[falken, 2014/12/15 06:20:20]

Ah I totally missed the point of your comment. OK, just comment is fine.

+    return;
   ServiceWorkerVersion* active_version = registration->active_version();
   DCHECK_EQ(active_version->status(), ServiceWorkerVersion::ACTIVATING);
   SetControllerVersionAttribute(active_version);