Enable magic window mode with new Gvr

chrome/android/java/src/org/chromium/chrome/browser/vr_shell/NonPresentingGvrContextInterface.java

+// Copyright 2016 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.
+
+package org.chromium.chrome.browser.vr_shell;
+
+/**
+ * Abstracts away the NonPresentingGvrContext class, which may or may not be present at runtime
+ * depending on compile flags.
+ */
+public interface NonPresentingGvrContextInterface {

[David Trainor- moved to gerrit, 2016/10/13 03:24:14]

Remove "Interface" and call the other class NonPresentingGvrContextImpl?

[bshe, 2016/10/13 14:06:28]

I copied this pattern from VrShellInterface and VrShell. I will do a follow up
CL to change file and class names to have a better isolation.

+    /**
+     * Returns the native gvr context.
+     */
+    long getNativeGvrContext();
+
+    /**
+     * Must be called when activity resumes.
+     */
+    void resume();
+
+    /**
+     * Must be called when activity pauses.
+     */
+    void pause();
+
+    /**
+     * Shutdown the native gvr context.
+     */
+    void shutdown();
+}