Implement the logic to kick off image decoding jobs for TileManager

cc/picture.h

 // Copyright 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.
 
 #ifndef CC_PICTURE_H_
 #define CC_PICTURE_H_
 
+#include <vector>
+
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
 #include "cc/cc_export.h"
 #include "skia/ext/refptr.h"
 #include "third_party/skia/include/core/SkPicture.h"
+#include "third_party/skia/include/core/SkPixelRef.h"
 #include "ui/gfx/rect.h"
 
 namespace cc {
 
 class ContentLayerClient;
 struct RenderingStats;
 
 class CC_EXPORT Picture
     : public base::RefCountedThreadSafe<Picture> {
 public:
   static scoped_refptr<Picture> Create(gfx::Rect layer_rect);
 
   const gfx::Rect& LayerRect() const { return layer_rect_; }
   const gfx::Rect& OpaqueRect() const { return opaque_rect_; }
 
   // Make a thread-safe clone for rasterizing with.
   scoped_refptr<Picture> Clone() const;
 
   // Record a paint operation. To be able to safely use this SkPicture for
   // playback on a different thread this can only be called once.
   void Record(ContentLayerClient*, RenderingStats&);
 
   // Has Record() been called yet?
   bool HasRecording() const { return picture_.get(); }
 
   // Raster this Picture's layer_rect into the given canvas.
   // Assumes contentsScale have already been applied.
   void Raster(SkCanvas* canvas);
 
+  std::vector<SkPixelRef*> GatherPixelRefs(const gfx::Rect& rect);
+
 private:
   Picture(gfx::Rect layer_rect);
   // This constructor assumes SkPicture is already ref'd and transfers
   // ownership to this picture.
   Picture(const skia::RefPtr<SkPicture>&,
           gfx::Rect layer_rect,
           gfx::Rect opaque_rect);
   ~Picture();
 
   gfx::Rect layer_rect_;
   gfx::Rect opaque_rect_;
   skia::RefPtr<SkPicture> picture_;
 
   friend class base::RefCountedThreadSafe<Picture>;
   DISALLOW_COPY_AND_ASSIGN(Picture);
 };
 
 }  // namespace cc
 
 #endif  // CC_PICTURE_H_