[Mac] Reduce timer CPU use in MessagePumpCFRunLoopBase.

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 60 matching lines @@
 // "NSAutoreleasePool" in such TUs. Finally, in Manual Retain Release (MRR)
 // Objective-C TUs, it is a type alias for NSAutoreleasePool. In all cases, a
 // method that takes or returns an NSAutoreleasePool* can use
 // AutoreleasePoolType* instead.
 #if !defined(__OBJC__) || __has_feature(objc_arc)
 class AutoreleasePoolType;
 #else   // !defined(__OBJC__) || __has_feature(objc_arc)
 typedef NSAutoreleasePool AutoreleasePoolType;
 #endif  // !defined(__OBJC__) || __has_feature(objc_arc)
 
-class MessagePumpCFRunLoopBase : public MessagePump {
+class BASE_EXPORT MessagePumpCFRunLoopBase : public MessagePump {
   // Needs access to CreateAutoreleasePool.
   friend class MessagePumpScopedAutoreleasePool;
+  friend class TestMessagePumpCFRunLoopBase;
+
  public:
   MessagePumpCFRunLoopBase();
   ~MessagePumpCFRunLoopBase() override;
 
   // Subclasses should implement the work they need to do in MessagePump::Run
   // in the DoRun method.  MessagePumpCFRunLoopBase::Run calls DoRun directly.
   // This arrangement is used because MessagePumpCFRunLoopBase needs to set
   // up and tear down things before and after the "meat" of DoRun.
   void Run(Delegate* delegate) override;
   virtual void DoRun(Delegate* delegate) = 0;
@@ skipping 12 matching lines @@
   // |delegateless_work_| is true.  |delegate| can be NULL.
   void SetDelegate(Delegate* delegate);
 
   // Return an autorelease pool to wrap around any work being performed.
   // In some cases, CreateAutoreleasePool may return nil intentionally to
   // preventing an autorelease pool from being created, allowing any
   // objects autoreleased by work to fall into the current autorelease pool.
   virtual AutoreleasePoolType* CreateAutoreleasePool();
 
  private:
+  // Marking timers as invalid at the right time helps significantly reduce
+  // power use (see the comment in RunDelayedWorkTimer()), however there is no
+  // public API for doing so. CFRuntime.h states that CFRuntimeBase, upon which
+  // the above timer invalidation functions are based, can change from release
+  // to release and should not be accessed directly (this struct last changed at
+  // least in 2008 in CF-476).
+  //
+  // This function uses private API to modify a test timer's valid state and
+  // uses public API to confirm that the private API changed the right bit.
+  static bool CanInvalidateCFRunLoopTimers();
+
+  // Sets a Core Foundation object's "invalid" bit to |valid|. Based on code
+  // from CFRunLoop.c.
+  static void ChromeCFRunLoopTimerSetValid(CFRunLoopTimerRef timer, bool valid);
+
   // Timer callback scheduled by ScheduleDelayedWork.  This does not do any
   // work, but it signals work_source_ so that delayed work can be performed
   // within the appropriate priority constraints.
   static void RunDelayedWorkTimer(CFRunLoopTimerRef timer, void* info);
 
   // Perform highest-priority work.  This is associated with work_source_
   // signalled by ScheduleWork or RunDelayedWorkTimer.  The static method calls
   // the instance method; the instance method returns true if it resignalled
   // work_source_ to be called again from the loop.
   static void RunWorkSource(void* info);
@@ skipping 219 matching lines @@
   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_