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

content/child/runtime_features.cc

Index: content/child/runtime_features.cc
diff --git a/content/child/runtime_features.cc b/content/child/runtime_features.cc
index 2698bf32ae15ff7f5d97eb0f07acad7f861612f9..81389a6ba4e72f962620be9b7032857dcd20ac99 100644
--- a/content/child/runtime_features.cc
+++ b/content/child/runtime_features.cc
@@ -313,6 +313,12 @@ void SetRuntimeFeaturesDefaultsAndUpdateFromArgs(
   if (base::FeatureList::IsEnabled(features::kGenericSensor))
     WebRuntimeFeatures::enableGenericSensor(true);
 
+  // Enable features which VrShell depends on.
+  if (base::FeatureList::IsEnabled(features::kVrShell)) {
+    WebRuntimeFeatures::enableGamepadExtensions(true);
+    WebRuntimeFeatures::enableWebVR(true);
+  }
+
   // Enable explicitly enabled features, and then disable explicitly disabled
   // ones.
   if (command_line.HasSwitch(switches::kEnableBlinkFeatures)) {