Add separate feature flag for VR CCT browsing.

chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java

 // 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.
 
 package org.chromium.chrome.browser.vr_shell;
 
 import android.app.Activity;
 import android.app.ActivityManager;
 import android.app.PendingIntent;
 import android.content.BroadcastReceiver;
@@ skipping 300 matching lines @@
 
         return sInstance;
     }
 
     private static boolean activitySupportsPresentation(Activity activity) {
         return activity instanceof ChromeTabbedActivity || activity instanceof CustomTabActivity
                 || activity instanceof WebappActivity;
     }
 
     private static boolean activitySupportsVrBrowsing(Activity activity) {
-        return activity instanceof ChromeTabbedActivity || activity instanceof CustomTabActivity;
+        if (activity instanceof ChromeTabbedActivity) return true;
+        if (activity instanceof CustomTabActivity) {
+            return ChromeFeatureList.isEnabled(ChromeFeatureList.VR_CUSTOM_TAB_BROWSING);
+        }
+        return false;
     }
 
     /**
      * @return A helper class for creating VR-specific classes that may not be available at compile
      * time.
      */
     private static VrClassesWrapper getVrClassesWrapper() {
         if (sInstance != null) return sInstance.mVrClassesWrapper;
         return createVrClassesWrapper();
     }
@@ skipping 658 matching lines @@
     private static native void nativeOnLibraryAvailable();
     private native void nativeSetPresentResult(long nativeVrShellDelegate, boolean result);
     private native void nativeDisplayActivate(long nativeVrShellDelegate);
     private native void nativeUpdateVSyncInterval(long nativeVrShellDelegate, long timebaseNanos,
             double intervalSeconds);
     private native void nativeOnPause(long nativeVrShellDelegate);
     private native void nativeOnResume(long nativeVrShellDelegate);
     private native void nativeUpdateNonPresentingContext(long nativeVrShellDelegate, long context);
     private native void nativeDestroy(long nativeVrShellDelegate);
 }