Add support for new scroll valuators coming from CMT

ui/views/events/event.h

Index: ui/views/events/event.h
diff --git a/ui/views/events/event.h b/ui/views/events/event.h
index c0cf2e0ea8dd11454c46aca92bcf080ac0e93d5f..4d0d2f16bb9120ebf307709488991b61174cda6b 100644
--- a/ui/views/events/event.h
+++ b/ui/views/events/event.h
@@ -410,6 +410,19 @@ class VIEWS_EXPORT DropTargetEvent : public LocatedEvent {
   DISALLOW_COPY_AND_ASSIGN(DropTargetEvent);
 };
 
+class VIEWS_EXPORT ScrollEvent : public MouseEvent {
+ public:
+  explicit ScrollEvent(const NativeEvent& native_event);
+  float x_offset() const { return x_offset_; }
+  float y_offset() const { return y_offset_; }
+
+ private:
+  float x_offset_;
+  float y_offset_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScrollEvent);
+};
+
 }  // namespace views
 
 #endif  // UI_VIEWS_EVENTS_EVENT_H_