[Reland] Post loading tasks on the appropriate WebFrameScheduler's queue

content/child/resource_dispatcher.cc

Index: content/child/resource_dispatcher.cc
diff --git a/content/child/resource_dispatcher.cc b/content/child/resource_dispatcher.cc
index baf79aece718232c05fc097c35ff775116d35817..7dbfe9eea22865598b67f4e4b770f8b409f259bb 100644
--- a/content/child/resource_dispatcher.cc
+++ b/content/child/resource_dispatcher.cc
@@ -114,7 +114,15 @@ bool ResourceDispatcher::OnMessageReceived(const IPC::Message& message) {
     }
   }
 
-  DispatchMessage(message);
+  // If the request is associated with a specific loading task queue then
+  // dispatch the message there, otherwise dispatch it here.

[Sami, 2015/09/25 13:31:27]

I guess the other alternative would be to dispatch this on the correct runner
from the IO thread. Would it make sense to have a message filter which does
that? That would avoid this extra main thread hop.

I was thinking back to your earlier patch that forwards ranges of IPC messages
to different task runners, but this would need to be more general since we need
to inspect the message before we can route it. Also, |request_info| is probably
not thread safe so we might need to be smarter about how we read it.

WDYT?

[alex clarke (OOO till 29th), 2015/09/28 17:24:53]

Done. Turned out to be much less invasive than I'd expected.

+  if (request_info->loading_task_queue) {
+    request_info->loading_task_queue->PostTask(
+        FROM_HERE, base::Bind(&ResourceDispatcher::DispatchMessage,
+                              base::Unretained(this), message));
+  } else {
+    DispatchMessage(message);
+  }
   return true;
 }
 
@@ -480,7 +488,8 @@ ResourceDispatcher::PendingRequestInfo::PendingRequestInfo(
     int origin_pid,
     const GURL& frame_origin,
     const GURL& request_url,
-    bool download_to_file)
+    bool download_to_file,
+    scoped_refptr<base::SingleThreadTaskRunner> loading_task_queue)
     : peer(peer),
       threaded_data_provider(NULL),
       resource_type(resource_type),
@@ -490,7 +499,8 @@ ResourceDispatcher::PendingRequestInfo::PendingRequestInfo(
       frame_origin(frame_origin),
       response_url(request_url),
       download_to_file(download_to_file),
-      request_start(base::TimeTicks::Now()) {
+      request_start(base::TimeTicks::Now()),
+      loading_task_queue(loading_task_queue) {
 }
 
 ResourceDispatcher::PendingRequestInfo::~PendingRequestInfo() {
@@ -588,7 +598,8 @@ int ResourceDispatcher::StartAsync(const RequestInfo& request_info,
                          request->origin_pid,
                          frame_origin,
                          request->url,
-                         request_info.download_to_file);
+                         request_info.download_to_file,
+                         request_info.loading_task_queue);
 
   message_sender_->Send(new ResourceHostMsg_RequestResource(
       request_info.routing_id, request_id, *request));