Add VrShell feature flag and wire it up to VrShell delegate.

chrome/browser/about_flags.cc

Index: chrome/browser/about_flags.cc
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index f82c43913c8f961e1c643904b8954a71038ba0d8..348b57b346ee4aaf8e56fcfe5703a35d4acbbec3 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -1597,6 +1597,11 @@ const FeatureEntry kFeatureEntries[] = {
     {"enable-webvr", IDS_FLAGS_WEBVR_NAME, IDS_FLAGS_WEBVR_DESCRIPTION, kOsAll,
      SINGLE_VALUE_TYPE(switches::kEnableWebVR)},
 #endif  // ENABLE_WEBVR
+#if defined(ENABLE_VR_SHELL)
+    {"enable-vr-shell", IDS_FLAGS_ENABLE_VR_SHELL_NAME,
+     IDS_FLAGS_ENABLE_VR_SHELL_DESCRIPTION, kOsAndroid,
+     FEATURE_VALUE_TYPE(features::kVrShell)},
+#endif  // ENABLE_VR_SHELL
 #if defined(OS_CHROMEOS)
     {"disable-accelerated-mjpeg-decode",
      IDS_FLAGS_ACCELERATED_MJPEG_DECODE_NAME,
@@ -1965,10 +1970,6 @@ const FeatureEntry kFeatureEntries[] = {
      IDS_FLAGS_FRAMEBUSTING_NAME, IDS_FLAGS_FRAMEBUSTING_DESCRIPTION, kOsAll,
      FEATURE_VALUE_TYPE(features::kFramebustingNeedsSameOriginOrUserGesture)},
 #if defined(OS_ANDROID)
-    {"enable-vr-shell", IDS_FLAGS_ENABLE_VR_SHELL_NAME,
-     IDS_FLAGS_ENABLE_VR_SHELL_DESCRIPTION, kOsAndroid,
-     ENABLE_DISABLE_VALUE_TYPE(switches::kEnableVrShell,
-                               switches::kDisableVrShell)},
     {"enable-android-pay-integration-v1",
      IDS_FLAGS_ENABLE_ANDROID_PAY_INTEGRATION_V1_NAME,
      IDS_FLAGS_ENABLE_ANDROID_PAY_INTEGRATION_V1_DESCRIPTION, kOsAndroid,