cc: Add image to rect map in DiscardableImageMap.

cc/playback/discardable_image_map.h

 // Copyright 2015 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_PLAYBACK_DISCARDABLE_IMAGE_MAP_H_
 #define CC_PLAYBACK_DISCARDABLE_IMAGE_MAP_H_
 
+#include <unordered_map>
 #include <utility>
 #include <vector>
 
 #include "cc/base/cc_export.h"
 #include "cc/base/rtree.h"
 #include "cc/playback/draw_image.h"
+#include "cc/playback/image_id.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "third_party/skia/include/core/SkRefCnt.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/size.h"
 
 namespace cc {
 
 // Helper function to apply the matrix to the rect and return the result.
 SkRect MapRect(const SkMatrix& matrix, const SkRect& src);
 
@@ skipping 15 matching lines @@
     std::unique_ptr<SkCanvas> metadata_canvas_;
   };
 
   DiscardableImageMap();
   ~DiscardableImageMap();
 
   bool empty() const { return all_images_.empty(); }
   void GetDiscardableImagesInRect(const gfx::Rect& rect,
                                   float contents_scale,
                                   std::vector<DrawImage>* images) const;
+  gfx::Rect GetRectForImage(ImageId image_id) const;
 
  private:
   friend class ScopedMetadataGenerator;
   friend class DiscardableImageMapTest;
 
   std::unique_ptr<SkCanvas> BeginGeneratingMetadata(const gfx::Size& bounds);
   void EndGeneratingMetadata();
 
   std::vector<std::pair<DrawImage, gfx::Rect>> all_images_;
+  std::unordered_map<ImageId, gfx::Rect> image_id_to_rect_;
+
   RTree images_rtree_;
 };
 
 }  // namespace cc
 
 #endif  // CC_PLAYBACK_DISCARDABLE_IMAGE_MAP_H_