Support NSFlagsChanged in ui::EventFromNative.

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 "ui/events/test/cocoa_test_event_utils.h"
 
 #include <stdint.h>
 
 #include "base/mac/scoped_cftyperef.h"
 #include "base/time/time.h"
@@ skipping 217 matching lines @@
                      modifierFlags:modifiers
                          timestamp:TimeIntervalSinceSystemStartup()
                       windowNumber:0
                            context:nil
                         characters:chars
        charactersIgnoringModifiers:chars
                          isARepeat:NO
                            keyCode:key_code];
 }
 
+NSEvent* KeyEventWithModifierOnly(unsigned short key_code,
+                                  NSUInteger modifiers) {
+  return [NSEvent keyEventWithType:NSFlagsChanged
+                          location:NSZeroPoint
+                     modifierFlags:modifiers
+                         timestamp:TimeIntervalSinceSystemStartup()
+                      windowNumber:0
+                           context:nil
+                        characters:@""
+       charactersIgnoringModifiers:@""
+                         isARepeat:NO
+                           keyCode:key_code];
+}
+
 static NSEvent* EnterExitEventWithType(NSEventType event_type) {
   return [NSEvent enterExitEventWithType:event_type
                                 location:NSZeroPoint
                            modifierFlags:0
                                timestamp:TimeIntervalSinceSystemStartup()
                             windowNumber:0
                                  context:nil
                              eventNumber:0
                           trackingNumber:0
                                 userData:NULL];
@@ skipping 105 matching lines @@
                                      context:nil
                                   characters:characters
                  charactersIgnoringModifiers:charactersIgnoringModifiers
                                    isARepeat:NO
                                      keyCode:(unsigned short)macKeycode];
 
   return event;
 }
 
 }  // namespace cocoa_test_event_utils