[vr] Introduce VrTabHelper

chrome/browser/android/vr_shell/vr_tab_helper.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 "chrome/browser/android/vr_shell/vr_tab_helper.h"
+
+#include "chrome/browser/android/vr_shell/vr_shell_delegate.h"
+#include "device/vr/android/gvr/gvr_delegate_provider.h"
+
+DEFINE_WEB_CONTENTS_USER_DATA_KEY(vr_shell::VrTabHelper);
+
+namespace vr_shell {
+
+VrTabHelper::VrTabHelper(content::WebContents* contents)
+    : content::WebContentsObserver(contents) {}
+VrTabHelper::~VrTabHelper() {}
+
+}  // namespace vr_shell