Fixed position layer counter-scroll with main thread scroll offset fractional part

cc/layers/layer_impl.h

 // Copyright 2011 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_LAYERS_LAYER_IMPL_H_
 #define CC_LAYERS_LAYER_IMPL_H_
 
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 383 matching lines @@
   gfx::ScrollOffset scroll_offset() const { return scroll_offset_; }
 
   gfx::ScrollOffset MaxScrollOffset() const;
   gfx::Vector2dF ClampScrollToMaxScrollOffset();
   void SetScrollbarPosition(ScrollbarLayerImplBase* scrollbar_layer,
                             LayerImpl* scrollbar_clip_layer,
                             bool on_resize) const;
   void SetScrollDelta(const gfx::Vector2dF& scroll_delta);
   gfx::Vector2dF ScrollDelta() const;
 
+  void SetMainScrollOffsetFractionalPart(const gfx::Vector2dF& scroll_offset) {
+    main_scroll_offset_fractional_part_ = scroll_offset;
+  }
+  gfx::Vector2dF MainScrollOffsetFracitionalPart() const {

[aelias_OOO_until_Jul13, 2015/01/28 02:04:00]

spelling: should be "Fractional", not "Fracitional"

[Yufeng Shen (Slow to review), 2015/01/28 22:28:09]

Done.

+    return main_scroll_offset_fractional_part_;
+  }
+
   gfx::ScrollOffset TotalScrollOffset() const;
 
   void SetSentScrollDelta(const gfx::Vector2dF& sent_scroll_delta);
   gfx::Vector2dF sent_scroll_delta() const { return sent_scroll_delta_; }
 
   // Returns the delta of the scroll that was outside of the bounds of the
   // initial scroll
   gfx::Vector2dF ScrollBy(const gfx::Vector2dF& scroll);
 
   void SetScrollClipLayer(int scroll_clip_layer_id);
@@ skipping 254 matching lines @@
   SkXfermode::Mode blend_mode_;
   gfx::PointF position_;
   gfx::Transform transform_;
 
   LayerPositionConstraint position_constraint_;
 
   gfx::Vector2dF scroll_delta_;
   gfx::Vector2dF sent_scroll_delta_;
   gfx::ScrollOffset last_scroll_offset_;
 
+  gfx::Vector2dF main_scroll_offset_fractional_part_;
+
   int num_descendants_that_draw_content_;
 
   // The global depth value of the center of the layer. This value is used
   // to sort layers from back to front.
   float draw_depth_;
 
   FilterOperations filters_;
   FilterOperations background_filters_;
 
  protected:
@@ skipping 43 matching lines @@
 
   std::vector<FrameTimingRequest> frame_timing_requests_;
   bool frame_timing_requests_dirty_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_IMPL_H_