VR: Further split common code from Android-specific code.

chrome/browser/android/vr_shell/ui_browser_interface.h

+// 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.
+
+#ifndef CHROME_BROWSER_ANDROID_VR_SHELL_UI_BROWSER_INTERFACE_H_
+#define CHROME_BROWSER_ANDROID_VR_SHELL_UI_BROWSER_INTERFACE_H_
+
+#include "chrome/browser/android/vr_shell/ui_unsupported_mode.h"
+
+namespace vr_shell {
+
+// An interface for the UI to communicate with VrShell.  Many of the functions
+// in this interface are proxies to methods on VrShell.
+class UiBrowserInterface {
+ public:
+  virtual ~UiBrowserInterface() = default;
+
+  virtual void ExitPresent() = 0;
+  virtual void ExitFullscreen() = 0;
+  virtual void NavigateBack() = 0;
+  virtual void ExitCct() = 0;
+  virtual void OnUnsupportedMode(UiUnsupportedMode mode) = 0;
+};
+
+}  // namespace vr_shell
+
+#endif  // CHROME_BROWSER_ANDROID_VR_SHELL_UI_BROWSER_INTERFACE_H_