MacViews: Add WidgetEventGenerator to abstract platform-specific event generation for tests.

ui/events/test/cocoa_test_event_utils.mm

 // Copyright 2014 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.
 
 #import <Cocoa/Cocoa.h>
 
 #include "ui/events/test/cocoa_test_event_utils.h"
 
 ScopedClassSwizzler::ScopedClassSwizzler(Class target, Class source,
                                          SEL selector) {
   old_selector_impl_ = class_getInstanceMethod(target, selector);
   new_selector_impl_ = class_getInstanceMethod(source, selector);
+  if (!old_selector_impl_ && !new_selector_impl_) {
+    // Try class methods.
+    old_selector_impl_ = class_getClassMethod(target, selector);
+    new_selector_impl_ = class_getClassMethod(source, selector);
+  }
   method_exchangeImplementations(old_selector_impl_, new_selector_impl_);
 }
 
 ScopedClassSwizzler::~ScopedClassSwizzler() {
   method_exchangeImplementations(old_selector_impl_, new_selector_impl_);
 }
 
 namespace cocoa_test_event_utils {
 
 NSEvent* MouseEventAtPoint(NSPoint point, NSEventType type,
@@ skipping 114 matching lines @@
                        modifierFlags:0
                            timestamp:0
                         windowNumber:0
                              context:nil
                              subtype:0
                                data1:0
                                data2:0];
 }
 
 }  // namespace cocoa_test_event_utils