Add a CFRunLoop mode for message loop tasks

base/message_loop/message_pump_mac.h

 // Copyright (c) 2012 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.
 
 // The basis for all native run loops on the Mac is the CFRunLoop.  It can be
 // used directly, it can be used as the driving force behind the similar
 // Foundation NSRunLoop, and it can be used to implement higher-level event
 // loops such as the NSApplication event loop.
 //
 // This file introduces a basic CFRunLoop-based implementation of the
@@ skipping 332 matching lines @@
 
   // Wrapper to query -[NSApp isHandlingSendEvent] from C++ code.
   // Requires NSApp to implement CrAppProtocol.
   static bool IsHandlingSendEvent();
 #endif  // !defined(OS_IOS)
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(MessagePumpMac);
 };
 
+// Tasks posted to the message loop are posted under this mode, as well
+// as kCFRunLoopCommonModes.
+extern const CFStringRef BASE_EXPORT kMessageLoopExclusiveRunLoopMode;
+
 }  // namespace base
 
 #endif  // BASE_MESSAGE_LOOP_MESSAGE_PUMP_MAC_H_