Support NSFlagsChanged in ui::EventFromNative.

ui/events/cocoa/cocoa_event_utils.h

 // 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.
 
 #ifndef UI_EVENTS_COCOA_COCOA_EVENT_UTILS_H_
 #define UI_EVENTS_COCOA_COCOA_EVENT_UTILS_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include "ui/events/events_export.h"
 
 namespace ui {
 
 // Conversion between wheel delta amounts and number of pixels to scroll.
 constexpr double kScrollbarPixelsPerCocoaTick = 40.0;
 
 // Converts the Cocoa |modifiers| bitsum into a ui::EventFlags bitsum.
 EVENTS_EXPORT int EventFlagsFromModifiers(NSUInteger modifiers);
 
 // Retrieves a bitsum of ui::EventFlags represented by |event|,
 // but instead use the modifier flags given by |modifiers|,
 // which is the same format as |-NSEvent modifierFlags|. This allows
 // substitution of the modifiers without having to create a new event from
 // scratch.
 EVENTS_EXPORT int EventFlagsFromNSEventWithModifiers(NSEvent* event,
                                                      NSUInteger modifiers);
+
+// Returns true for |NSKeyUp| and for |NSFlagsChanged| when modifier key was
+// released.
+EVENTS_EXPORT bool IsKeyUpEvent(NSEvent* event);
+
 }  // namespace ui
 
 #endif  // UI_EVENTS_COCOA_COCOA_EVENT_UTILS_H_