Message pump for Mac UI loop starves delayed work

base/message_pump_mac.mm

 // Copyright (c) 2008 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_pump_mac.h"
 
 #import <AppKit/AppKit.h>
 #import <Foundation/Foundation.h>
 #include <IOKit/IOMessage.h>
 #include <IOKit/pwr_mgt/IOPMLib.h>
@@ skipping 62 matching lines @@
   CFRunLoopSourceContext source_context = CFRunLoopSourceContext();
   source_context.info = this;
   source_context.perform = RunWorkSource;
   work_source_ = CFRunLoopSourceCreate(NULL,  // allocator
                                        1,     // priority
                                        &source_context);
   CFRunLoopAddSource(run_loop_, work_source_, kCFRunLoopCommonModes);
 
   source_context.perform = RunDelayedWorkSource;
   delayed_work_source_ = CFRunLoopSourceCreate(NULL,  // allocator
-                                               2,     // priority
+                                               1,     // priority
                                                &source_context);
   CFRunLoopAddSource(run_loop_, delayed_work_source_, kCFRunLoopCommonModes);
 
   source_context.perform = RunIdleWorkSource;
   idle_work_source_ = CFRunLoopSourceCreate(NULL,  // allocator
                                             3,     // priority
                                             &source_context);
   CFRunLoopAddSource(run_loop_, idle_work_source_, kCFRunLoopCommonModes);
 
   source_context.perform = RunNestingDeferredWorkSource;
@@ skipping 664 matching lines @@
 // static
 MessagePump* MessagePumpMac::Create() {
   if ([NSThread isMainThread]) {
     return new MessagePumpNSApplication;
   }
 
   return new MessagePumpNSRunLoop;
 }
 
 }  // namespace base