HTML5 Video runs into super full screen mode

bug:5569146

Browser change
https://android-git.corp.google.com/g/#/c/151035/

Change-Id: Ib8449a670caf4aa2b540a170ed5e9f6adea2b12e

Author: Teng-Hui Zhu

core/java/android/webkit/HTML5VideoFullScreen.java

@@ -261,6 +261,8 @@ public void enterFullScreenVideoState(int layerId,
         mLayout.addView(getSurfaceView(), layoutParams);
 
         mLayout.setVisibility(View.VISIBLE);
+        mLayout.setSystemUiVisibility(View.SYSTEM_UI_FLAG_LOW_PROFILE
+                | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION);
 
         WebChromeClient client = webView.getWebChromeClient();
         if (client != null) {