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..16fde2c497a4cdfdcc1c88e218abe089094e6eb5 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.railMode() != PlatformWheelEventRailModeVertical;
+    bool canScrollY = m_scrollableArea->userInputScrollable(VerticalScrollbar)
+        && e.railMode() != PlatformWheelEventRailModeHorizontal;
 
     // Accept the event if we are scrollable in that direction and can still
     // scroll any further.