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

ui/views/view.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #define _USE_MATH_DEFINES // For VC++ to get M_PI. This has to be first.
 
 #include "ui/views/view.h"
 
 #include <algorithm>
 #include <cmath>
@@ skipping 852 matching lines @@
   return false;
 }
 
 bool View::OnMouseWheel(const ui::MouseWheelEvent& event) {
   return false;
 }
 
 void View::OnKeyEvent(ui::KeyEvent* event) {
 }
 
-ui::EventResult View::OnMouseEvent(ui::MouseEvent* event) {
-  return ui::ER_UNHANDLED;
+void View::OnMouseEvent(ui::MouseEvent* event) {
 }
 
 void View::OnScrollEvent(ui::ScrollEvent* event) {
 }
 
 void View::OnTouchEvent(ui::TouchEvent* event) {
 }
 
 void View::OnGestureEvent(ui::GestureEvent* event) {
 }
@@ skipping 1278 matching lines @@
   ConvertPointToWidget(this, &widget_location);
   GetWidget()->RunShellDrag(this, data, widget_location, drag_operations,
       source);
   return true;
 #else
   return false;
 #endif  // !defined(OS_MACOSX)
 }
 
 }  // namespace views