cc: Add image decode control in the compositor.

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 <utility>
 #include <vector>
 
 #include "base/memory/scoped_ptr.h"
 #include "cc/base/cc_export.h"
 #include "cc/base/rtree.h"
 #include "cc/playback/draw_image.h"
 #include "third_party/skia/include/core/SkPicture.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/size.h"
 
 class SkImage;
 
 namespace cc {
 
+// Helper function to apply the matrix to the rect and return the result.
+SkRect MapRect(const SkMatrix& matrix, const SkRect& src);
+
+// Helper funciton to extract a scale from the matrix. Returns true on success
+// and false on failure.
+bool ExtractScale(const SkMatrix& matrix, SkSize* scale);
+
+// Helper function to compute the new rect bounds adjusted for both the current
+// paint and all of the saved paints. Returns true on success and false on
+// failure.
+bool ComputeRectBoundsFromPaint(const SkRect& rect,
+                                const SkPaint* current_paint,
+                                const std::vector<const SkPaint*>& saved_paints,
+                                SkRect* paint_bounds);
+
 // This class is used for generating discardable images data (see DrawImage
 // for the type of data it stores). It allows the client to query a particular
 // rect and get back a list of DrawImages in that rect.
 class CC_EXPORT DiscardableImageMap {
  public:
   class CC_EXPORT ScopedMetadataGenerator {
    public:
     ScopedMetadataGenerator(DiscardableImageMap* image_map,
                             const gfx::Size& bounds);
     ~ScopedMetadataGenerator();
@@ skipping 21 matching lines @@
   scoped_ptr<SkCanvas> BeginGeneratingMetadata(const gfx::Size& bounds);
   void EndGeneratingMetadata();
 
   std::vector<std::pair<DrawImage, gfx::Rect>> all_images_;
   RTree images_rtree_;
 };
 
 }  // namespace cc
 
 #endif  // CC_PLAYBACK_DISCARDABLE_IMAGE_MAP_H_