[Mac] Use a native MessagePump instead of a MessagePumpDefault

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 211 matching lines @@
 #if defined(OS_IOS) || defined(OS_MACOSX)
 #define MESSAGE_PUMP_UI scoped_ptr<MessagePump>(MessagePumpMac::Create())
 #elif defined(OS_NACL)
 // Currently NaCl doesn't have a UI MessageLoop.
 // TODO(abarth): Figure out if we need this.
 #define MESSAGE_PUMP_UI scoped_ptr<MessagePump>()
 #else
 #define MESSAGE_PUMP_UI scoped_ptr<MessagePump>(new MessagePumpForUI())
 #endif
 
+#if defined(OS_MACOSX)
+  // Use an OS native runloop on Mac to support timer coalescing.
+  #define MESSAGE_PUMP_DEFAULT scoped_ptr<MessagePump>(MessagePumpMac::Create())

[Mark Mentovai, 2014/06/11 21:59:42]

We may want a MessagePumpCFRunLoop instead of a MessagePumpNSRunLoop. I don’t
think we’ve ever gauged performance. You should look into this.

+#else
+  #define MESSAGE_PUMP_DEFAULT scoped_ptr<MessagePump>(new MessagePumpDefault())
+#endif
+
   if (type == MessageLoop::TYPE_UI) {
     if (message_pump_for_ui_factory_)
       return message_pump_for_ui_factory_();
     return MESSAGE_PUMP_UI;
   }
   if (type == MessageLoop::TYPE_IO)
     return scoped_ptr<MessagePump>(new MessagePumpForIO());
 
 #if defined(OS_ANDROID)
   if (type == MessageLoop::TYPE_JAVA)
     return scoped_ptr<MessagePump>(new MessagePumpForUI());
 #endif
 
   DCHECK_EQ(MessageLoop::TYPE_DEFAULT, type);
-  return scoped_ptr<MessagePump>(new MessagePumpDefault());
+  return MESSAGE_PUMP_DEFAULT;
 }
 
 void MessageLoop::AddDestructionObserver(
     DestructionObserver* destruction_observer) {
   DCHECK_EQ(this, current());
   destruction_observers_.AddObserver(destruction_observer);
 }
 
 void MessageLoop::RemoveDestructionObserver(
     DestructionObserver* destruction_observer) {
@@ skipping 476 matching lines @@
       persistent,
       mode,
       controller,
       delegate);
 }
 #endif
 
 #endif  // !defined(OS_NACL)
 
 }  // namespace base