[Android] Add test case for hasEnteredFullscreen and leaveFullscreen.

This patch is to add test case for hasEnteredFullscreen() and
leaveFullscreen().
Click the button to enter fullscreen, exit fullscreen or call leaveFullscreen,
verify the value of hasEnteredFullscreen().
Merge pull request #2344 from wuhengzhi/fullscreen_auto_test

[Android] Add test case for hasEnteredFullscreen and leaveFullscreen.