Adds button to VRShell menu mode, which lets the user manually exit WebVR presentation.

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

Index: chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java b/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java
index af104f87ea807d8484f72366883393b6cf7b2f52..ba65d1b234a0083b8974eec5f0588814adaa7996 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java
@@ -521,19 +521,13 @@ public class VrShellDelegate implements ApplicationStatus.ActivityStateListener
     }
 
     @CalledByNative
-    private boolean exitWebVR() {
+    private boolean exitWebVRPresent() {
         if (!mInVr) return false;
         mVrShell.setWebVrModeEnabled(false);
         if (mVrSupportLevel == VR_CARDBOARD) {
             // Transition screen is not available for Cardboard only (non-Daydream) devices.
             // TODO(bshe): Fix this once b/33490788 is fixed.
             shutdownVR(false /* isPausing */, false /* showTransition */);
-        } else {
-            // TODO(bajones): Once VR Shell can be invoked outside of WebVR this
-            // should no longer exit the shell outright. Need a way to determine
-            // how VrShell was created.
-            shutdownVR(

[mthiesse, 2017/03/30 15:36:57]

We still need to call shutdownVR if VR Shell isn't enabled so that we don't
return to VR Shell.

[tiborg, 2017/03/30 20:53:29]

Done.

-                    false /* isPausing */, !isVrShellEnabled(mVrSupportLevel) /* showTransition */);
         }
         return true;
     }