Consolidate two IsArcWindow functions to reduce code duplication

components/arc/arc_util.cc

 // 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 "components/arc/arc_util.h"
 
 #include <string>
 
+#include "ash/shared/app_types.h"
+#include "ash/wm_window.h"
 #include "base/command_line.h"
 #include "base/feature_list.h"
 #include "chromeos/chromeos_switches.h"
 #include "components/user_manager/user_manager.h"
 
 namespace arc {
 
 namespace {
 
 // This is for finch. See also crbug.com/633704 for details.
@@ skipping 85 matching lines @@
              chromeos::switches::kArcAvailability) ==
          kAvailabilityOfficiallySupportedWithActiveDirectory;
 }
 
 bool IsArcOptInVerificationDisabled() {
   const auto* command_line = base::CommandLine::ForCurrentProcess();
   return command_line->HasSwitch(
       chromeos::switches::kDisableArcOptInVerification);
 }
 
+bool IsArcAppWindow(aura::Window* window) {
+  // The getter returns nullptr when |window| is nullptr.
+  ash::WmWindow* wm_window = ash::WmWindow::Get(window);
+  if (!wm_window)
+    return false;
+  return wm_window->GetAppType() == static_cast<int>(ash::AppType::ARC_APP);
+}
+
 }  // namespace arc