[Mac] Re-Enable timer coalescing on Mac.

base/message_loop/message_pump_mac.mm

 // 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.
 
 #import "base/message_loop/message_pump_mac.h"
 
 #include <dlfcn.h>
 #import <Foundation/Foundation.h>
 
 #include <limits>
@@ skipping 54 matching lines @@
 
 #if !defined(OS_IOS)
 // Set to true if MessagePumpMac::Create() is called before NSApp is
 // initialized.  Only accessed from the main thread.
 bool g_not_using_cr_app = false;
 #endif
 
 // Call through to CFRunLoopTimerSetTolerance(), which is only available on
 // OS X 10.9.
 void SetTimerTolerance(CFRunLoopTimerRef timer, CFTimeInterval tolerance) {
-// TODO(jeremy): Temporarily disabled in order to gauge net effect of timer
-// coalescing.
-#if 0
   typedef void (*CFRunLoopTimerSetTolerancePtr)(CFRunLoopTimerRef timer,
       CFTimeInterval tolerance);
 
   static CFRunLoopTimerSetTolerancePtr settimertolerance_function_ptr;
 
   static dispatch_once_t get_timer_tolerance_function_ptr_once;
   dispatch_once(&get_timer_tolerance_function_ptr_once, ^{
       NSBundle* bundle =[NSBundle
         bundleWithPath:@"/System/Library/Frameworks/CoreFoundation.framework"];
       const char* path = [[bundle executablePath] fileSystemRepresentation];
       CHECK(path);
       void* library_handle = dlopen(path, RTLD_LAZY | RTLD_LOCAL);
       CHECK(library_handle) << dlerror();
       settimertolerance_function_ptr =
           reinterpret_cast<CFRunLoopTimerSetTolerancePtr>(
               dlsym(library_handle, "CFRunLoopTimerSetTolerance"));
 
       dlclose(library_handle);
   });
 
   if (settimertolerance_function_ptr)
     settimertolerance_function_ptr(timer, tolerance);
-#endif
 }
 
 }  // namespace
 
 // static
 const CFStringRef kMessageLoopExclusiveRunLoopMode =
     CFSTR("kMessageLoopExclusiveRunLoopMode");
 
 // A scoper for autorelease pools created from message pump run loops.
 // Avoids dirtying up the ScopedNSAutoreleasePool interface for the rare
@@ skipping 661 matching lines @@
     [NSApplication sharedApplication];
     g_not_using_cr_app = true;
     return new MessagePumpNSApplication;
 #endif
   }
 
   return new MessagePumpNSRunLoop;
 }
 
 }  // namespace base