Revert of Don't show video fullscreen until DidEnterFullscreen() is called (https://codereview.chromium.org/277823002/)

Reason for revert:
this breaks webview. DidEnterFullscreen will never be received since webview doesn't support fullscreen api. As a result, video won't enter fullscreen.

Original issue's description:
> Don't show video fullscreen until DidEnterFullscreen() is called
> 
> For fullscreen video on android, We call showFullscreenOverlay() too early.
> We should wait until DidEnterFullscreen() gets called, and then we should let the video element to request the surface view.
> Otherwise, if enterFullscreenForElement fails, we will incorrectly showing the fullscreen video in the background.
> This CL also removes the hideFullscreenOverlay() call since this is no longer needed.
> When exiting fullscreen, video view will automatically be destroyed.
> 
> BUG=367346
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=173917

TBR=aelias@chromium.org,trchen@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=367346

Review URL: https://codereview.chromium.org/284913002

git-svn-id: svn://svn.chromium.org/blink/trunk@173975 bbb929c8-8fbe-4397-9dbb-9b2b20218538