Pause drawing webvr when the App button is pressed

chrome/browser/android/vr_shell/BUILD.gn

 # 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.
 
 import("//build/config/android/rules.gni")
 import("//chrome/common/features.gni")
 import("//device/vr/features/features.gni")
 import("//testing/test.gni")
 
 assert(enable_vr)
@@ skipping 34 matching lines @@
       "ui_elements/transient_security_warning.cc",
       "ui_elements/transient_security_warning.h",
       "ui_elements/ui_element.cc",
       "ui_elements/ui_element.h",
       "ui_interface.cc",
       "ui_interface.h",
       "ui_scene.cc",
       "ui_scene.h",
       "ui_scene_manager.cc",
       "ui_scene_manager.h",
+      "vr_browser_interface.h",
       "vr_compositor.cc",
       "vr_compositor.h",
       "vr_controller.cc",
       "vr_controller.h",
       "vr_controller_model.cc",
       "vr_controller_model.h",
       "vr_gl_thread.cc",
       "vr_gl_thread.h",
       "vr_gl_util.cc",
       "vr_gl_util.h",
@@ skipping 52 matching lines @@
 }
 
 if (enable_vr) {
   test("vr_shell_unittests") {
     sources = [
       "fps_meter_unittest.cc",
       "gltf_parser_unittest.cc",
       "test/paths.cc",
       "test/paths.h",
       "ui_elements/ui_element_unittest.cc",
+      "ui_scene_manager_unittest.cc",
       "ui_scene_unittest.cc",
     ]
 
     deps = [
       ":vr_common",
       "//base/test:run_all_unittests",
       "//base/test:test_support",
       "//chrome/browser",
+      "//testing/gmock",
       "//testing/gtest",
       "//third_party/WebKit/public:blink",
       "//ui/gfx/geometry",
     ]
 
     # Ensure libgvr static library appears before gcc library in linking order.
     # See https://crbug.com/704305 for details.
     libs =
         [ "//third_party/gvr-android-sdk/libgvr_shim_static_${current_cpu}.a" ]
 
     data = [
       "test/data/sample_inline.gltf",
       "test/data/sample_external.gltf",
       "test/data/sample.bin",
       "test/data/sample.glb",
     ]
   }
 }