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

base/message_loop/message_loop.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/message_loop/message_loop.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/compiler_specific.h"
@@ skipping 82 matching lines @@
 #elif defined(OS_POSIX)
 typedef MessagePumpLibevent MessagePumpForIO;
 #endif
 
 #if !defined(OS_NACL_SFI)
 MessagePumpForIO* ToPumpIO(MessagePump* pump) {
   return static_cast<MessagePumpForIO*>(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() {
 }
 
 MessageLoop::TaskObserver::~TaskObserver() {
 }
 
 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)
       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) {
   Init();
-
   pump_ = CreateMessagePumpForType(type).Pass();
 }
 
 MessageLoop::MessageLoop(scoped_ptr<MessagePump> pump)
     : pump_(pump.Pass()),
       type_(TYPE_CUSTOM),
 #if defined(OS_WIN)
       pending_high_res_tasks_(0),
       in_high_res_mode_(false),
 #endif
@@ skipping 238 matching lines @@
   // queue.
   return incoming_task_queue_->IsIdleForTesting();
 }
 
 //------------------------------------------------------------------------------
 
 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(
       new ThreadTaskRunnerHandle(message_loop_proxy_));
 }
 
 void MessageLoop::RunHandler() {
   DCHECK_EQ(this, current());
 
   StartHistogrammer();
@@ skipping 33 matching lines @@
   }
 #endif
 
   // Execute the task and assume the worst: It is probably not reentrant.
   nestable_tasks_allowed_ = false;
 
   HistogramEvent(kTaskRunEvent);
 
   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));
 
   nestable_tasks_allowed_ = true;
 }
 
 bool MessageLoop::DeferOrRunPendingTask(const PendingTask& pending_task) {
   if (pending_task.nestable || run_loop_->run_depth_ == 1) {
     RunTask(pending_task);
@@ skipping 256 matching lines @@
       persistent,
       mode,
       controller,
       delegate);
 }
 #endif
 
 #endif  // !defined(OS_NACL_SFI)
 
 }  // namespace base