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 26 matching lines @@
       "vr_shell.cc",
       "vr_shell.h",
       "vr_shell_delegate.cc",
       "vr_shell_delegate.h",
       "vr_shell_renderer.cc",
       "vr_shell_renderer.h",
       "vr_web_contents_observer.cc",
       "vr_web_contents_observer.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 29 matching lines @@
 
     deps = [
       ":vr_common",
       "//base/test:run_all_unittests",
       "//base/test:test_support",
       "//testing/gtest",
       "//ui/gfx/geometry",
     ]
   }
 }