Correctly detect when switching back from full screen

In full screen mode, the play message can be trigger, that means we can't
assume that the play message only comes from inline mode.

bug:4498120

Change-Id: Ibf85bb74778df207a6ce786dc63b0845356a281c
diff --git a/core/java/android/webkit/HTML5VideoViewProxy.java b/core/java/android/webkit/HTML5VideoViewProxy.java
index aa254d9d..d0237b5 100644
--- a/core/java/android/webkit/HTML5VideoViewProxy.java
+++ b/core/java/android/webkit/HTML5VideoViewProxy.java
@@ -173,9 +173,7 @@
             boolean backFromFullScreenMode = false;
             if (mHTML5VideoView != null) {
                 currentVideoLayerId = mHTML5VideoView.getVideoLayerId();
-                if (mHTML5VideoView instanceof HTML5VideoFullScreen) {
-                    backFromFullScreenMode = true;
-                }
+                backFromFullScreenMode = mHTML5VideoView.fullScreenExited();
             }
 
             if (backFromFullScreenMode