Revert of Revert of ServiceWorker: Use scheduler's default task queue for posting tasks on main thread (patchset #1 id:1 of https://codereview.chromium.org/954993002/)

Reason for revert:
Test is still flaky, even after reverting this one. For instance

http://build.chromium.org/p/chromium.win/builders/Vista%20Tests%20%281%29/builds/53768

Original issue's description:
> Revert of ServiceWorker: Use scheduler's default task queue for posting tasks on main thread (patchset #1 id:1 of https://codereview.chromium.org/958523002/)
>
> Reason for revert:
> Highly speculative revert after views_unittests broke on win7:
>
> http://build.chromium.org/p/chromium.win/builders/Win7%20Tests%20%28dbg%29%281%29/builds/35660
>
> c:\b\build\slave\win_builder__dbg_\build\src\ui\views\accessibility\native_view_accessibility_win_unittest.cc(190): error: Value of: infobar_accessible.IsSameObject(targets[0])
>
> This patch does change task queuing, which makes it seem slightly more likely to break stuff than the others in the blamelist.
>
> Original issue's description:
> > ServiceWorker: Use scheduler's default task queue for posting tasks on main thread
> >
> > This fixes a task ordering bug between WebMessagePortChannelImpl and
> > ServiceWorkerScriptContext. The former posts tasks via the Blink
> > scheduler's default task queue, and the latter was using the MessageLoop
> > directly. This patch makes tasks from service worker to the main thread
> > go through the scheduler.
> >
> > BUG=460833
> > TEST=http/tests/serviceworker/postmessage-msgport-to-client.html
> >
> > Committed: https://crrev.com/a7fe515e3ca07e260b58ebf460f842601266ed87
> > Cr-Commit-Position: refs/heads/master@{#318022}
>
> TBR=kinuko@chromium.org,skyostil@chromium.org,ksakamoto@chromium.org
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=460833
>
> Committed: https://crrev.com/64250e71c15dfe3576d8e4077e4dfb04f9382482
> Cr-Commit-Position: refs/heads/master@{#318040}

TBR=kinuko@chromium.org,skyostil@chromium.org,ksakamoto@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=460833

Review URL: https://codereview.chromium.org/957583003

Cr-Commit-Position: refs/heads/master@{#318058}

3 files changed, 17 insertions, 15 deletions

diff --git a/content/renderer/service_worker/embedded_worker_context_client.cc b/content/renderer/service_worker/embedded_worker_context_client.cc
index 2173ced..b84340b 100644
--- a/content/renderer/service_worker/embedded_worker_context_client.cc
+++ b/content/renderer/service_worker/embedded_worker_context_client.cc
@@ -106,7 +106,7 @@ EmbeddedWorkerContextClient::EmbeddedWorkerContextClient(
       script_url_(script_url),
       worker_devtools_agent_route_id_(worker_devtools_agent_route_id),
       sender_(ChildThreadImpl::current()->thread_safe_sender()),
-      main_thread_proxy_(base::MessageLoopProxy::current()),
+      main_thread_task_runner_(RenderThreadImpl::current()->GetTaskRunner()),
       weak_factory_(this) {
   TRACE_EVENT_ASYNC_BEGIN0("ServiceWorker",
                            "EmbeddedWorkerContextClient::StartingWorkerContext",
@@ -180,7 +180,7 @@ void EmbeddedWorkerContextClient::workerReadyForInspection() {
 }
 
 void EmbeddedWorkerContextClient::workerContextFailedToStart() {
-  DCHECK(main_thread_proxy_->RunsTasksOnCurrentThread());
+  DCHECK(main_thread_task_runner_->RunsTasksOnCurrentThread());
   DCHECK(!script_context_);
 
   Send(new EmbeddedWorkerHostMsg_WorkerScriptLoadFailed(embedded_worker_id_));
@@ -243,7 +243,7 @@ void EmbeddedWorkerContextClient::workerContextDestroyed() {
 
   // Now we should be able to free the WebEmbeddedWorker container on the
   // main thread.
-  main_thread_proxy_->PostTask(
+  main_thread_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&CallWorkerContextDestroyedOnMainThread,
                  embedded_worker_id_));
@@ -355,7 +355,7 @@ void EmbeddedWorkerContextClient::didHandleCrossOriginConnectEvent(
 blink::WebServiceWorkerNetworkProvider*
 EmbeddedWorkerContextClient::createServiceWorkerNetworkProvider(
     blink::WebDataSource* data_source) {
-  DCHECK(main_thread_proxy_->RunsTasksOnCurrentThread());
+  DCHECK(main_thread_task_runner_->RunsTasksOnCurrentThread());
 
   // Create a content::ServiceWorkerNetworkProvider for this data source so
   // we can observe its requests.
@@ -380,7 +380,7 @@ EmbeddedWorkerContextClient::createServiceWorkerNetworkProvider(
 
 blink::WebServiceWorkerProvider*
 EmbeddedWorkerContextClient::createServiceWorkerProvider() {
-  DCHECK(main_thread_proxy_->RunsTasksOnCurrentThread());
+  DCHECK(main_thread_task_runner_->RunsTasksOnCurrentThread());
   DCHECK(provider_context_);
 
   // Blink is responsible for deleting the returned object.
diff --git a/content/renderer/service_worker/embedded_worker_context_client.h b/content/renderer/service_worker/embedded_worker_context_client.h
index 1f7ac8d..89000a7 100644
--- a/content/renderer/service_worker/embedded_worker_context_client.h
+++ b/content/renderer/service_worker/embedded_worker_context_client.h
@@ -14,7 +14,7 @@
 #include "url/gurl.h"
 
 namespace base {
-class MessageLoopProxy;
+class SingleThreadTaskRunner;
 class TaskRunner;
 }
 
@@ -130,8 +130,8 @@ class EmbeddedWorkerContextClient
   // TODO: Implement DevTools related method overrides.
 
   int embedded_worker_id() const { return embedded_worker_id_; }
-  base::MessageLoopProxy* main_thread_proxy() const {
-    return main_thread_proxy_.get();
+  base::SingleThreadTaskRunner* main_thread_task_runner() const {
+    return main_thread_task_runner_.get();
   }
   ThreadSafeSender* thread_safe_sender() { return sender_.get(); }
 
@@ -148,7 +148,7 @@ class EmbeddedWorkerContextClient
   const GURL script_url_;
   const int worker_devtools_agent_route_id_;
   scoped_refptr<ThreadSafeSender> sender_;
-  scoped_refptr<base::MessageLoopProxy> main_thread_proxy_;
+  scoped_refptr<base::SingleThreadTaskRunner> main_thread_task_runner_;
   scoped_refptr<base::TaskRunner> worker_task_runner_;
 
   scoped_ptr<ServiceWorkerScriptContext> script_context_;
diff --git a/content/renderer/service_worker/service_worker_script_context.cc b/content/renderer/service_worker/service_worker_script_context.cc
index 61c83be..74df548 100644
--- a/content/renderer/service_worker/service_worker_script_context.cc
+++ b/content/renderer/service_worker/service_worker_script_context.cc
@@ -253,7 +253,7 @@ void ServiceWorkerScriptContext::PostMessageToDocument(
   // messages for MessagePort (e.g. QueueMessages) are sent from main thread
   // (with thread hopping), so we need to do the same thread hopping here not
   // to overtake those messages.
-  embedded_context_->main_thread_proxy()->PostTask(
+  embedded_context_->main_thread_task_runner()->PostTask(
       FROM_HERE,
       base::Bind(&SendPostMessageToDocumentOnMainThread,
                  make_scoped_refptr(embedded_context_->thread_safe_sender()),
@@ -268,7 +268,7 @@ void ServiceWorkerScriptContext::PostCrossOriginMessageToClient(
   // messages for MessagePort (e.g. QueueMessages) are sent from main thread
   // (with thread hopping), so we need to do the same thread hopping here not
   // to overtake those messages.
-  embedded_context_->main_thread_proxy()->PostTask(
+  embedded_context_->main_thread_task_runner()->PostTask(
       FROM_HERE,
       base::Bind(&SendCrossOriginMessageToClientOnMainThread,
                  make_scoped_refptr(embedded_context_->thread_safe_sender()),
@@ -412,11 +412,12 @@ void ServiceWorkerScriptContext::OnPostMessage(
                "ServiceWorkerScriptContext::OnPostEvent");
   std::vector<WebMessagePortChannelImpl*> ports;
   if (!sent_message_port_ids.empty()) {
-    base::MessageLoopProxy* loop_proxy = embedded_context_->main_thread_proxy();
+    base::SingleThreadTaskRunner* task_runner =
+        embedded_context_->main_thread_task_runner();
     ports.resize(sent_message_port_ids.size());
     for (size_t i = 0; i < sent_message_port_ids.size(); ++i) {
       ports[i] = new WebMessagePortChannelImpl(
-          new_routing_ids[i], sent_message_port_ids[i], loop_proxy);
+          new_routing_ids[i], sent_message_port_ids[i], task_runner);
     }
   }
 
@@ -438,11 +439,12 @@ void ServiceWorkerScriptContext::OnCrossOriginMessageToWorker(
                "ServiceWorkerScriptContext::OnCrossOriginMessageToWorker");
   std::vector<WebMessagePortChannelImpl*> ports;
   if (!sent_message_port_ids.empty()) {
-    base::MessageLoopProxy* loop_proxy = embedded_context_->main_thread_proxy();
+    base::SingleThreadTaskRunner* task_runner =
+        embedded_context_->main_thread_task_runner();
     ports.resize(sent_message_port_ids.size());
     for (size_t i = 0; i < sent_message_port_ids.size(); ++i) {
       ports[i] = new WebMessagePortChannelImpl(
-          new_routing_ids[i], sent_message_port_ids[i], loop_proxy);
+          new_routing_ids[i], sent_message_port_ids[i], task_runner);
     }
   }