Implement WebVR presentation pausing for VR Shell Menu Mode

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("//testing/test.gni")
 
 assert(enable_vr_shell || enable_webvr)
 
@@ skipping 23 matching lines @@
     "vr_math.cc",
     "vr_math.h",
     "vr_shell.cc",
     "vr_shell.h",
     "vr_shell_delegate.cc",
     "vr_shell_delegate.h",
     "vr_shell_renderer.cc",
     "vr_shell_renderer.h",
   ]
 
+  if (enable_vr_shell) {
+    defines += [ "ENABLE_VR_SHELL" ]
+  }
   if (enable_vr_shell_ui_dev) {
     assert(enable_vr_shell)
     defines += [ "ENABLE_VR_SHELL_UI_DEV" ]
   }
 
   deps = [
     ":vr_shell_jni_headers",
     "//base",
     "//cc",
     "//content/public/browser",
@@ skipping 26 matching lines @@
 
     deps = [
       ":vr_common",
       "//base/test:run_all_unittests",
       "//base/test:test_support",
       "//testing/gtest",
       "//ui/gfx/geometry",
     ]
   }
 }