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

cc/layers/layer.h

Index: cc/layers/layer.h
diff --git a/cc/layers/layer.h b/cc/layers/layer.h
index e4344127c7643976dff8a2231d7ad44438bf0d1c..43037de55675e0f8db87dc5b674445cf3163aa05 100644
--- a/cc/layers/layer.h
+++ b/cc/layers/layer.h
@@ -266,6 +266,10 @@ class CC_EXPORT Layer : public base::RefCounted<Layer>,
 
   RenderSurface* render_surface() const { return render_surface_.get(); }
   void SetScrollOffset(const gfx::ScrollOffset& scroll_offset);
+  void SetScrollOffsetFractionalPart(
+      const gfx::Vector2dF& scroll_offset_fractional_part);
+  gfx::Vector2dF MainScrollOffsetFractionalPart() const;
+
   gfx::ScrollOffset scroll_offset() const { return scroll_offset_; }
   void SetScrollOffsetFromImplSide(const gfx::ScrollOffset& scroll_offset);
 
@@ -636,6 +640,7 @@ class CC_EXPORT Layer : public base::RefCounted<Layer>,
   gfx::Size bounds_;
 
   gfx::ScrollOffset scroll_offset_;
+  gfx::Vector2dF scroll_offset_fractional_part_;
   // This variable indicates which ancestor layer (if any) whose size,
   // transformed relative to this layer, defines the maximum scroll offset for
   // this layer.