[Approach 3] Pre-allocate IncomigTaskQueue before MessageLoop for faster thread startup

base/message_loop/message_loop.cc

Index: base/message_loop/message_loop.cc
diff --git a/base/message_loop/message_loop.cc b/base/message_loop/message_loop.cc
index eb0f968849485ea73ef8a1aab9094bb9527af403..4bb312777324036ce820e5365f81fb4fb50a64fe 100644
--- a/base/message_loop/message_loop.cc
+++ b/base/message_loop/message_loop.cc
@@ -100,10 +100,25 @@ MessagePumpForIO* ToPumpIO(MessagePump* pump) {
 }
 #endif  // !defined(OS_NACL_SFI)
 
+MessageLoop::Type GetMessageLoopType(const MessageLoop::Options& options) {
+  if (options.message_pump_factory.is_null())
+    return options.message_loop_type;
+  return MessageLoop::TYPE_CUSTOM;
+}
+
 }  // namespace
 
 //------------------------------------------------------------------------------
 
+MessageLoop::Options::Options()
+    : message_loop_type(MessageLoop::TYPE_DEFAULT) {
+}
+
+MessageLoop::Options::~Options() {
+}
+
+//------------------------------------------------------------------------------
+
 MessageLoop::TaskObserver::TaskObserver() {
 }
 
@@ -115,6 +130,26 @@ MessageLoop::DestructionObserver::~DestructionObserver() {
 
 //------------------------------------------------------------------------------
 
+MessageLoop::MessageLoop(const Options& options)
+    : type_(GetMessageLoopType(options)),
+#if defined(OS_WIN)
+      pending_high_res_tasks_(0),
+      in_high_res_mode_(false),
+#endif
+      nestable_tasks_allowed_(true),
+#if defined(OS_WIN)
+      os_modal_loop_(false),
+#endif  // OS_WIN
+      message_histogram_(NULL),
+      run_loop_(NULL),
+      incoming_task_queue_(options.incoming_task_queue) {
+  if (!options.message_pump_factory.is_null())
+    pump_ = options.message_pump_factory.Run();
+  else
+    pump_ = CreateMessagePumpForType(type_);
+  Init();
+}
+
 MessageLoop::MessageLoop(Type type)
     : type_(type),
 #if defined(OS_WIN)
@@ -128,7 +163,6 @@ MessageLoop::MessageLoop(Type type)
       message_histogram_(NULL),
       run_loop_(NULL) {
   Init();
-
   pump_ = CreateMessagePumpForType(type).Pass();
 }
 
@@ -387,7 +421,9 @@ void MessageLoop::Init() {
   DCHECK(!current()) << "should only have one message loop per thread";
   lazy_tls_ptr.Pointer()->Set(this);
 
-  incoming_task_queue_ = new internal::IncomingTaskQueue(this);
+  if (!incoming_task_queue_)
+    incoming_task_queue_ = new internal::IncomingTaskQueue();
+  incoming_task_queue_->StartScheduling(this);
   message_loop_proxy_ =
       new internal::MessageLoopProxyImpl(incoming_task_queue_);
   thread_task_runner_handle_.reset(
@@ -441,7 +477,7 @@ void MessageLoop::RunTask(const PendingTask& pending_task) {
 
   FOR_EACH_OBSERVER(TaskObserver, task_observers_,
                     WillProcessTask(pending_task));
-  task_annotator_.RunTask(
+  task_annotator()->RunTask(
       "MessageLoop::PostTask", "MessageLoop::RunTask", pending_task);
   FOR_EACH_OBSERVER(TaskObserver, task_observers_,
                     DidProcessTask(pending_task));