Don't dispatch vrdisplayactivate event if the page that listens for it is invisible

chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrDaydreamApi.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;
 
 import android.app.PendingIntent;
 import android.content.ComponentName;
 import android.content.Intent;
 
@@ skipping 39 matching lines @@
 
     /**
      * Sets VR Mode to |enabled|.
      */
     void setVrModeEnabled(boolean enabled);
 
     /**
      * @return Whether the current Viewer is a Daydream Viewer.
      */
     Boolean isDaydreamCurrentViewer();
+
+    /**
+     * Launch the stereoscopic, 3D VR launcher homescreen.
+     */
+    void launchVrHomescreen();
 }