cc: Make picture pile base thread safe.

cc/resources/picture_pile_base.h

 // Copyright 2013 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 CC_RESOURCES_PICTURE_PILE_BASE_H_
 #define CC_RESOURCES_PICTURE_PILE_BASE_H_
 
 #include <bitset>
 #include <list>
 #include <utility>
 
 #include "base/containers/hash_tables.h"
 #include "base/memory/ref_counted.h"
 #include "cc/base/cc_export.h"
 #include "cc/base/region.h"
 #include "cc/base/tiling_data.h"
 #include "cc/resources/picture.h"
 #include "ui/gfx/geometry/size.h"
 
 namespace base {
 namespace debug {
 class TracedValue;
 }
 class Value;
 }
 
 namespace cc {
 
-class CC_EXPORT PicturePileBase : public base::RefCounted<PicturePileBase> {
+class CC_EXPORT PicturePileBase
+    : public base::RefCountedThreadSafe<PicturePileBase> {
  public:
   PicturePileBase();
   explicit PicturePileBase(const PicturePileBase* other);
 
   gfx::Size tiling_size() const { return tiling_.tiling_size(); }
   void SetMinContentsScale(float min_contents_scale);
 
   // If non-empty, all pictures tiles inside this rect are recorded. There may
   // be recordings outside this rect, but everything inside the rect is
   // recorded.
@@ skipping 89 matching lines @@
   // positive.
   bool has_any_recordings_;
   bool has_text_;
   bool is_mask_;
   bool is_solid_color_;
   SkColor solid_color_;
 
  private:
   void SetBufferPixels(int buffer_pixels);
 
-  friend class base::RefCounted<PicturePileBase>;
+  friend class base::RefCountedThreadSafe<PicturePileBase>;
   DISALLOW_COPY_AND_ASSIGN(PicturePileBase);
 };
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_PICTURE_PILE_BASE_H_