events: Update mouse-event handlers to not return EventResult.

ui/base/events/event_dispatcher_unittest.cc

Index: ui/base/events/event_dispatcher_unittest.cc
diff --git a/ui/base/events/event_dispatcher_unittest.cc b/ui/base/events/event_dispatcher_unittest.cc
index 41eed0952d7f8be927f192939a7058c9c1cdd6ff..4b61cb4bd16bfd9e6dbb4a56babb4ccf7232b734 100644
--- a/ui/base/events/event_dispatcher_unittest.cc
+++ b/ui/base/events/event_dispatcher_unittest.cc
@@ -85,9 +85,9 @@ class TestEventHandler : public EventHandler {
     SetStatusOnEvent(event);
   }
 
-  virtual EventResult OnMouseEvent(MouseEvent* event) OVERRIDE {
+  virtual void OnMouseEvent(MouseEvent* event) OVERRIDE {
     ReceivedEvent(event);
-    return event_result_;
+    SetStatusOnEvent(event);
   }
 
   virtual void OnScrollEvent(ScrollEvent* event) OVERRIDE {