Fix compile error for MacOSX10.11.sdk using static_cast<CGEventFlags>

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 135 matching lines @@
   int32_t wheel1 = static_cast<int>(delta_y);
   int32_t wheel2 = static_cast<int>(delta_x);
   CGScrollEventUnit units =
       has_precise_deltas ? kCGScrollEventUnitPixel : kCGScrollEventUnitLine;
   base::ScopedCFTypeRef<CGEventRef> scroll(CGEventCreateScrollWheelEvent(
       nullptr, units, wheel_count, wheel1, wheel2));
   CGEventSetLocation(scroll, ScreenPointFromWindow(window_point, window));
 
   // Always set event flags, otherwise +[NSEvent eventWithCGEvent:] populates
   // flags from current keyboard state which can make tests flaky.
-  CGEventSetFlags(scroll, 0);
+  CGEventSetFlags(scroll, static_cast<CGEventFlags>(0));
 
   if (has_precise_deltas) {
     // kCGScrollWheelEventIsContinuous is -[NSEvent hasPreciseScrollingDeltas].
     // CGEventTypes.h says it should be non-zero for pixel-based scrolling.
     // Verify that CGEventCreateScrollWheelEvent() set it.
     DCHECK_EQ(1, CGEventGetIntegerValueField(scroll,
                                              kCGScrollWheelEventIsContinuous));
   }
 
   // Don't set phase information when neither.
@@ skipping 186 matching lines @@
                                      context:nil
                                   characters:characters
                  charactersIgnoringModifiers:charactersIgnoringModifiers
                                    isARepeat:NO
                                      keyCode:(unsigned short)macKeycode];
 
   return event;
 }
 
 }  // namespace cocoa_test_event_utils