Account for scroll origin in scroll animators.

third_party/WebKit/Source/platform/scroll/ScrollAnimatorCompositorCoordinator.cpp

Index: third_party/WebKit/Source/platform/scroll/ScrollAnimatorCompositorCoordinator.cpp
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollAnimatorCompositorCoordinator.cpp b/third_party/WebKit/Source/platform/scroll/ScrollAnimatorCompositorCoordinator.cpp
index 294fcbeee926d2f6e577430edac2f6cdd08a84fd..b340b18f3654ca6fb8f8cf9c40a38979ff1be625 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollAnimatorCompositorCoordinator.cpp
+++ b/third_party/WebKit/Source/platform/scroll/ScrollAnimatorCompositorCoordinator.cpp
@@ -227,4 +227,16 @@ CompositorAnimationPlayer* ScrollAnimatorCompositorCoordinator::compositorPlayer
     return m_compositorPlayer.get();
 }
 
+FloatPoint ScrollAnimatorCompositorCoordinator::compositorOffsetFromBlinkOffset(FloatPoint offset)
+{
+    offset.moveBy(scrollableArea()->scrollOrigin());
+    return offset;
+}
+
+FloatPoint ScrollAnimatorCompositorCoordinator::blinkOffsetFromCompositorOffset(FloatPoint offset)
+{
+    offset.moveBy(-scrollableArea()->scrollOrigin());
+    return offset;
+}
+
 } // namespace blink