aw: Fix hardware init/tear down in pop up flow

aw: Fix hardware init/tear down in pop up flow

Previously we did not call onDetached on old native AwContents,
which now no longer cleans up hardware resources correctly.

This also had the side effect that the following onAttach with the new
native AwContents is ignored in java code due to attach/detach mismatch.

As make onDetached more strict with respect to ordering. And lock to
protect variable accessed on multiple threads.

Also need to ensure we never requestDrawGL on the blank native
AwContents that's destroyed during pop up.

BUG=376622
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=272500

[boliu, 2014-05-23 02:51:42]

I'll leave the state in the internal bug

[boliu, 2014-05-23 03:09:52]

Actually figured out our problem, and did a fix without involving frameworks
change. I'll update the internal bug. Feel free to review + cq.

[benm (inactive), 2014-05-23 09:36:38]

lgtm

[commit-bot: I haz the power, 2014-05-23 09:37:19]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/boliu@chromium.org/288983007/20001

[commit-bot: I haz the power, 2014-05-23 11:55:50]

Change committed as 272500