[Mac] Maximise timer slack for background tabs

base/message_loop/message_pump_mac.h

Index: base/message_loop/message_pump_mac.h
diff --git a/base/message_loop/message_pump_mac.h b/base/message_loop/message_pump_mac.h
index afdd7d11fc9cca0faae37f445c40547e99fa3356..6667279691afe1a26d4a51e8362ca4e9e19e01f5 100644
--- a/base/message_loop/message_pump_mac.h
+++ b/base/message_loop/message_pump_mac.h
@@ -37,6 +37,7 @@
 #include <CoreFoundation/CoreFoundation.h>
 
 #include "base/memory/weak_ptr.h"
+#include "base/message_loop/timer_slack.h"
 
 #if defined(__OBJC__)
 #if defined(OS_IOS)
@@ -93,6 +94,7 @@ class MessagePumpCFRunLoopBase : public MessagePump {
 
   virtual void ScheduleWork() OVERRIDE;
   virtual void ScheduleDelayedWork(const TimeTicks& delayed_work_time) OVERRIDE;
+  virtual void SetTimerSlack(TimerSlack timer_slack) OVERRIDE;
 
  protected:
   // Accessors for private data members to be used by subclasses.
@@ -195,6 +197,8 @@ class MessagePumpCFRunLoopBase : public MessagePump {
   // See PowerStateNotification.
   CFAbsoluteTime delayed_work_fire_time_;
 
+  base::TimerSlack timer_slack_;
+
   // The recursion depth of the currently-executing CFRunLoopRun loop on the
   // run loop's thread.  0 if no run loops are running inside of whatever scope
   // the object was created in.