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

cc/layers/layer_impl.h

Index: cc/layers/layer_impl.h
diff --git a/cc/layers/layer_impl.h b/cc/layers/layer_impl.h
index f52b5de77ce21807418f2b26e0d19c41b6f03449..0380c630b84c95c8106138ace7e182288883ccbf 100644
--- a/cc/layers/layer_impl.h
+++ b/cc/layers/layer_impl.h
@@ -401,6 +401,13 @@ class CC_EXPORT LayerImpl : public LayerAnimationValueObserver,
   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);
@@ -675,6 +682,8 @@ class CC_EXPORT LayerImpl : public LayerAnimationValueObserver,
   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