Make DisplayLinkMac RefCountedThreadSafe

ui/accelerated_widget_mac/display_link_mac.h

 // Copyright 2014 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.
 
 #ifndef UI_ACCELERATED_WIDGET_MAC_DISPLAY_LINK_MAC_H_
 #define UI_ACCELERATED_WIDGET_MAC_DISPLAY_LINK_MAC_H_
 
 #include <map>
 #include <QuartzCore/CVDisplayLink.h>
 
 #include "base/lazy_instance.h"
 #include "base/mac/scoped_typeref.h"
 #include "base/memory/ref_counted.h"
 #include "base/synchronization/lock.h"
 #include "base/time/time.h"
 #include "base/timer/timer.h"
 #include "ui/accelerated_widget_mac/accelerated_widget_mac_export.h"
 
 namespace base {
 class SingleThreadTaskRunner;
 }
 
 namespace ui {
 
-class ACCELERATED_WIDGET_MAC_EXPORT DisplayLinkMac :
-    public base::RefCounted<DisplayLinkMac> {
+class ACCELERATED_WIDGET_MAC_EXPORT DisplayLinkMac
+    : public base::RefCountedThreadSafe<DisplayLinkMac> {
  public:
   static scoped_refptr<DisplayLinkMac> GetForDisplay(
       CGDirectDisplayID display_id);
 
   // Get vsync scheduling parameters.
   bool GetVSyncParameters(
       base::TimeTicks* timebase,
       base::TimeDelta* interval);
 
   // The vsync parameters are cached, because re-computing them is expensive.
   // The parameters also skew over time (astonishingly quickly -- 0.1 msec per
   // second), so, use this method to tell the display link the current time.
   // If too much time has elapsed since the last time the vsync parameters were
   // calculated, re-calculate them.
   void NotifyCurrentTime(const base::TimeTicks& now);
 
  private:
-  friend class base::RefCounted<DisplayLinkMac>;
+  friend class base::RefCountedThreadSafe<DisplayLinkMac>;
 
   DisplayLinkMac(
       CGDirectDisplayID display_id,
       base::ScopedTypeRef<CVDisplayLinkRef> display_link);
   virtual ~DisplayLinkMac();
 
   void StartOrContinueDisplayLink();
   void StopDisplayLink();
   void Tick(const CVTimeStamp& time);
 
@@ skipping 34 matching lines @@
 
   // Each display link instance consumes a non-negligible number of cycles, so
   // make all display links on the same screen share the same object.
   typedef std::map<CGDirectDisplayID, DisplayLinkMac*> DisplayMap;
   static base::LazyInstance<DisplayMap> display_map_;
 };
 
 }  // ui
 
 #endif  // UI_ACCELERATED_WIDGET_MAC_DISPLAY_LINK_MAC_H_