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..0c8d653e279ca6fa13430c3c38d9f5514bd0e459 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 +521,11 @@ 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(
-                    false /* isPausing */, !isVrShellEnabled(mVrSupportLevel) /* showTransition */);
+        if (!isVrShellEnabled(mVrSupportLevel)) {
+            shutdownVR(false /* isPausing */, true /* showTransition */);
         }
         return true;
     }
@@ -654,6 +646,8 @@ public class VrShellDelegate implements ApplicationStatus.ActivityStateListener
         if (!mInVr) return;
         mInVr = false;
         mRequestedWebVR = false;
+        // Transition screen is not available for Cardboard only (non-Daydream) devices.
+        // TODO(bshe): Fix this once b/33490788 is fixed.
         boolean transition = mVrSupportLevel == VR_DAYDREAM && showTransition;
         if (!isPausing) {
             if (!transition || !mVrDaydreamApi.exitFromVr(EXIT_VR_RESULT, new Intent())) {