Improve PictureLayerTiling::CoverageIterator to handle rounding more precisely

cc/base/tiling_data.h

 // Copyright 2010 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_BASE_TILING_DATA_H_
 #define CC_BASE_TILING_DATA_H_
 
 #include <utility>
 
 #include "base/logging.h"
 #include "cc/base/cc_export.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/size.h"
 
 namespace gfx {
+class RectF;
 class Vector2d;
 }
 
 namespace cc {
 
 class CC_EXPORT TilingData {
  public:
   TilingData();
   TilingData(const gfx::Size& max_texture_size,
              const gfx::Size& tiling_size,
@@ skipping 28 matching lines @@
   gfx::Rect ExpandRectIgnoringBordersToTileBounds(const gfx::Rect& rect) const;
   gfx::Rect ExpandRectToTileBounds(const gfx::Rect& rect) const;
 
   gfx::Rect TileBounds(int i, int j) const;
   gfx::Rect TileBoundsWithBorder(int i, int j) const;
   int TilePositionX(int x_index) const;
   int TilePositionY(int y_index) const;
   int TileSizeX(int x_index) const;
   int TileSizeY(int y_index) const;
 
+  gfx::RectF TexelExtent(int i, int j) const;
+
   // Difference between TileBound's and TileBoundWithBorder's origin().
   gfx::Vector2d TextureOffset(int x_index, int y_index) const;
 
   class CC_EXPORT BaseIterator {
    public:
     operator bool() const { return index_x_ != -1 && index_y_ != -1; }
 
     int index_x() const { return index_x_; }
     int index_y() const { return index_y_; }
     std::pair<int, int> index() const {
@@ skipping 162 matching lines @@
   int border_texels_;
 
   // These are computed values.
   int num_tiles_x_;
   int num_tiles_y_;
 };
 
 }  // namespace cc
 
 #endif  // CC_BASE_TILING_DATA_H_