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

ui/aura/gestures/gesture_recognizer_unittest.cc

Index: ui/aura/gestures/gesture_recognizer_unittest.cc
diff --git a/ui/aura/gestures/gesture_recognizer_unittest.cc b/ui/aura/gestures/gesture_recognizer_unittest.cc
index 59a2e75d7f7cbd87987e37360331be5b4337a687..6156b4cb3e959b3db0b8bb5003a13b1a42c90df5 100644
--- a/ui/aura/gestures/gesture_recognizer_unittest.cc
+++ b/ui/aura/gestures/gesture_recognizer_unittest.cc
@@ -373,7 +373,7 @@ class GestureEventSynthDelegate : public TestWindowDelegate {
   bool mouse_release() const { return mouse_release_; }
   bool double_click() const { return double_click_; }
 
-  virtual ui::EventResult OnMouseEvent(ui::MouseEvent* event) OVERRIDE {
+  virtual void OnMouseEvent(ui::MouseEvent* event) OVERRIDE {
     switch (event->type()) {
       case ui::ET_MOUSE_PRESSED:
         double_click_ = event->flags() & ui::EF_IS_DOUBLE_CLICK;
@@ -394,7 +394,7 @@ class GestureEventSynthDelegate : public TestWindowDelegate {
       default:
         NOTREACHED();
     }
-    return ui::ER_HANDLED;
+    event->SetHandled();
   }
 
  private: