VR: Hide 2D screenshot when resuming activities in VR and hide 2D UI while loading VR UI.

chrome/android/java/res/anim/stay_hidden.xml

Index: chrome/android/java/res/anim/stay_hidden.xml
diff --git a/chrome/android/java/res/anim/stay_hidden.xml b/chrome/android/java/res/anim/stay_hidden.xml
new file mode 100644
index 0000000000000000000000000000000000000000..be44bde0130ea61565fe7b4b632c4b4deac0c53b
--- /dev/null
+++ b/chrome/android/java/res/anim/stay_hidden.xml
@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- 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.
+-->
+
+<!-- The delay here must be long enough for the Activity being resumed to draw
+     its first frame of UI. This is to avoid showing stale 2D screenshots when
+     launching Chrome in VR. Note that the larger this value is, the more
+     latency we add to resuming Chrome after going through the Daydream Device
+     ON flow. -->
+<alpha xmlns:android="http://schemas.android.com/apk/res/android"
+        android:interpolator="@android:anim/linear_interpolator"
+        android:fromAlpha="0" android:toAlpha="0"
+        android:duration="500" />