Do not use overlays when VR shell is enabled.

chrome/android/java/src/org/chromium/chrome/browser/fullscreen/FullscreenHtmlApiHandler.java

Index: chrome/android/java/src/org/chromium/chrome/browser/fullscreen/FullscreenHtmlApiHandler.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/fullscreen/FullscreenHtmlApiHandler.java b/chrome/android/java/src/org/chromium/chrome/browser/fullscreen/FullscreenHtmlApiHandler.java
index b016c1cf5091136364099c9df0ff9b6d351b0493..00c29036d1363433b13ae68c3113a0e38fc69099 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/fullscreen/FullscreenHtmlApiHandler.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/fullscreen/FullscreenHtmlApiHandler.java
@@ -17,6 +17,7 @@ import android.view.View.OnLayoutChangeListener;
 import android.view.Window;
 import android.view.WindowManager;
 
+import org.chromium.base.Log;
 import org.chromium.chrome.R;
 import org.chromium.chrome.browser.tab.Tab;
 import org.chromium.content.browser.ContentViewCore;
@@ -184,6 +185,7 @@ public class FullscreenHtmlApiHandler {
      * @param enabled Whether to enable persistent fullscreen mode.
      */
     public void setPersistentFullscreenMode(boolean enabled) {
+        Log.d("amp_log", "Set persistent full screen: " + enabled);
         if (mIsPersistentMode == enabled) return;
 
         mIsPersistentMode = enabled;
@@ -254,6 +256,7 @@ public class FullscreenHtmlApiHandler {
      * @param tab The tab that is entering fullscreen.
      */
     public void enterFullscreen(final Tab tab) {
+        Log.d("amp_log", "Enter fullscreen, tab: " + tab);
         ContentViewCore contentViewCore = tab.getContentViewCore();
         if (contentViewCore == null) return;
         final View contentView = contentViewCore.getContainerView();