views: Stop dispatching scroll-gesture events if the scroll-begin event wasn't handled.

ui/views/widget/root_view.cc

Index: ui/views/widget/root_view.cc
diff --git a/ui/views/widget/root_view.cc b/ui/views/widget/root_view.cc
index 12c2d12cbb37feb7b0a530af2899544f72ae886e..2a71020447a758d17911b55e522cdecbeae00b9b 100644
--- a/ui/views/widget/root_view.cc
+++ b/ui/views/widget/root_view.cc
@@ -288,6 +288,17 @@ void RootView::DispatchGestureEvent(ui::GestureEvent* event) {
     return;
   }
 
+  // If there was no handler for a SCROLL_BEGIN event, then subsequent scroll
+  // events are not dispatched to any views.
+  switch (event->type()) {
+    case ui::ET_GESTURE_SCROLL_UPDATE:
+    case ui::ET_GESTURE_SCROLL_END:
+    case ui::ET_SCROLL_FLING_START:
+      return;
+    default:
+      break;
+  }
+
   // Walk up the tree until we find a view that wants the gesture event.
   for (gesture_handler_ = GetEventHandlerForPoint(event->location());
       gesture_handler_ && (gesture_handler_ != this);