Service Worker: Add metrics and timeout for starting a Service Worker.

content/renderer/service_worker/embedded_worker_context_client.cc

Index: content/renderer/service_worker/embedded_worker_context_client.cc
diff --git a/content/renderer/service_worker/embedded_worker_context_client.cc b/content/renderer/service_worker/embedded_worker_context_client.cc
index 2173cedeb59ad6dd5433434a5c31fe09509b1f12..1559a38fa52342ec2d726e472a6f69307c10a3b6 100644
--- a/content/renderer/service_worker/embedded_worker_context_client.cc
+++ b/content/renderer/service_worker/embedded_worker_context_client.cc
@@ -208,13 +208,6 @@ void EmbeddedWorkerContextClient::workerContextStarted(
       WorkerTaskRunner::Instance()->CurrentWorkerId(),
       provider_context_->provider_id()));
 
-  // Schedule a task to send back WorkerStarted asynchronously,
-  // so that at the time we send it we can be sure that the worker
-  // script has been evaluated and worker run loop has been started.
-  worker_task_runner_->PostTask(
-      FROM_HERE,
-      base::Bind(&EmbeddedWorkerContextClient::SendWorkerStarted,
-                 weak_factory_.GetWeakPtr()));
   TRACE_EVENT_ASYNC_STEP_INTO0(
       "ServiceWorker",
       "EmbeddedWorkerContextClient::StartingWorkerContext",
@@ -225,6 +218,13 @@ void EmbeddedWorkerContextClient::workerContextStarted(
 void EmbeddedWorkerContextClient::didEvaluateWorkerScript(bool success) {
   Send(new EmbeddedWorkerHostMsg_WorkerScriptEvaluated(
       embedded_worker_id_, success));
+
+  // Schedule a task to send back WorkerStarted asynchronously,
+  // so that at the time we send it we can be sure that the
+  // worker run loop has been started.
+  worker_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&EmbeddedWorkerContextClient::SendWorkerStarted,
+                            weak_factory_.GetWeakPtr()));

[kinuko, 2015/03/02 03:19:33]

Did you need to move this method? Could you explain a bit?

[falken, 2015/03/02 04:19:17]

It's just a cleanup. It was pretty confusing to reason about the message order
with the current code. Now it should be more clear the order is ScriptLoaded,
ScriptEvaluated, WorkerStarted.

[kinuko, 2015/03/02 06:13:19]

I see. We probably don't need to call the SendWorkerStarted asynchronously in
the new code?

[falken, 2015/03/02 06:33:16]

Yes I think the only reason we'd send async is if something happens
synchronously after evaluate() that we want to make sure finishes, which
probably isn't the case. I think WorkerScriptEvaluated and WorkerStarted could
probably be combined to the same message.

 }
 
 void EmbeddedWorkerContextClient::willDestroyWorkerContext() {