[Android] Add AppMenu touch duration metric.

chrome/browser/android/appmenu/app_menu_drag_helper.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 CHROME_BROWSER_ANDROID_APPMENU_APP_MENU_DRAG_HELPER_H_
+#define CHROME_BROWSER_ANDROID_APPMENU_APP_MENU_DRAG_HELPER_H_
+
+#include "base/android/jni_android.h"
+
+namespace appmenu {
+namespace android {
+
+bool RegisterAppMenuDragHelper(JNIEnv* env);
+
+}  // namespace android
+}  // namespace appmenu
+
+#endif  // CHROME_BROWSER_ANDROID_APPMENU_APP_MENU_DRAG_HELPER_H_