Delegate WebSocket message handlers to the loading task runner

content/child/websocket_dispatcher.cc

Index: content/child/websocket_dispatcher.cc
diff --git a/content/child/websocket_dispatcher.cc b/content/child/websocket_dispatcher.cc
index 9fc3370bb65d8bcc1b380761dba11efcf43103f9..54d9c1a18e84392ae123937c06ddc35f29950e11 100644
--- a/content/child/websocket_dispatcher.cc
+++ b/content/child/websocket_dispatcher.cc
@@ -7,6 +7,7 @@
 #include <stdint.h>
 #include <map>
 
+#include "base/bind.h"
 #include "base/logging.h"
 #include "content/child/websocket_bridge.h"
 #include "content/common/websocket_messages.h"
@@ -15,7 +16,8 @@
 
 namespace content {
 
-WebSocketDispatcher::WebSocketDispatcher() : channel_id_max_(0) {}
+WebSocketDispatcher::WebSocketDispatcher() : channel_id_max_(0) {
+}
 
 WebSocketDispatcher::~WebSocketDispatcher() {}
 
@@ -49,10 +51,22 @@ bool WebSocketDispatcher::OnMessageReceived(const IPC::Message& msg) {
       return false;
   }
 
+  loading_task_runner_->PostTask(FROM_HERE,

[Sami, 2016/05/23 09:56:07]

I guess what will end up happening here is that OnMessageReceived() will first
get called on the main thread and schedule this PostTask, which will also happen
on the main thread. Depending on how busy the main thread is this could add
significant delays to WebSocket messages.

A better alternative would be to turn WebSocketDispatcher into a IPC message
filter and have it PostTask to the loading task queue from the IO thread. I'm
not sure if we need to do that refactoring now, but I would suggest giving it
some thought (and adding a TODO at least).

+      base::Bind(&WebSocketDispatcher::OnMessageReceivedOnLoadingTaskRunner,
+                 base::Unretained(this), msg));
+  return true;
+}
+
+void WebSocketDispatcher::SetLoadingTaskRunner(
+    scoped_refptr<base::SingleThreadTaskRunner> loading_task_runner) {
+  loading_task_runner_ = loading_task_runner;
+}
+
+void WebSocketDispatcher::OnMessageReceivedOnLoadingTaskRunner(
+    IPC::Message msg) {
   WebSocketBridge* bridge = GetBridge(msg.routing_id(), msg.type());
-  if (!bridge)
-    return true;
-  return bridge->OnMessageReceived(msg);
+  if (bridge)
+    bridge->OnMessageReceived(msg);
 }
 
 WebSocketBridge* WebSocketDispatcher::GetBridge(int channel_id, uint32_t type) {