Add CrAppProtocol for headless on Mac

headless/lib/browser/headless_shell_application_mac.mm

+// Copyright 2017 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.
+
+#include "headless/lib/browser/headless_shell_application_mac.h"
+
+#include "base/auto_reset.h"
+
+@implementation HeadlessShellCrApplication
+
+- (BOOL)isHandlingSendEvent {
+  return handlingSendEvent_;
+}
+
+- (void)sendEvent:(NSEvent*)event {
+  base::AutoReset<BOOL> scoper(&handlingSendEvent_, YES);
+  [super sendEvent:event];
+}
+
+- (void)setHandlingSendEvent:(BOOL)handlingSendEvent {
+  handlingSendEvent_ = handlingSendEvent;
+}
+
+@end