Cherry-pick: [Android WebView] Early out DrawGL if not attached to window

Cherry-pick of crrev.com/r224307

BUG: 10839187

Original Description:

We release GL when we are detached from window, so calling DrawGL
while detached is causing crash.

Also take this opportunity move GL initialization to Draw mode and
not invoke mode.

Change-Id: Ica7e8460d2e7269948e74815b5bdd2baa86b6a5f
1 file changed