Add rails to input wheel events.

Source/platform/scroll/ScrollAnimator.cpp

Index: Source/platform/scroll/ScrollAnimator.cpp
diff --git a/Source/platform/scroll/ScrollAnimator.cpp b/Source/platform/scroll/ScrollAnimator.cpp
index 02a42413630d94ca11128bb8c406a6b4512975f3..dca16c9d5506a3d91869e6f9799e34db5d1247b7 100644
--- a/Source/platform/scroll/ScrollAnimator.cpp
+++ b/Source/platform/scroll/ScrollAnimator.cpp
@@ -74,8 +74,10 @@ void ScrollAnimator::scrollToOffsetWithoutAnimation(const FloatPoint& offset)
 
 ScrollResult ScrollAnimator::handleWheelEvent(const PlatformWheelEvent& e)
 {
-    bool canScrollX = m_scrollableArea->userInputScrollable(HorizontalScrollbar);
-    bool canScrollY = m_scrollableArea->userInputScrollable(VerticalScrollbar);
+    bool canScrollX = m_scrollableArea->userInputScrollable(HorizontalScrollbar)
+        && e.railsMode() != PlatformEvent::RailsModeVertical;
+    bool canScrollY = m_scrollableArea->userInputScrollable(VerticalScrollbar)
+        && e.railsMode() != PlatformEvent::RailsModeHorizontal;
 
     // Accept the event if we are scrollable in that direction and can still
     // scroll any further.