[Athena] Fix potential crash when overview window is deleted

[Athena] Fix potential crash when overview window is deleted

Delete the window immediately in WindowOverviewModeImpl::CloseDragWindow() and
use wm::ScopedHidingAnimationSettings to make then hide animation look right.
This fixes a potential crash if overview mode is exited while a window is
animating closed.

BUG=409724
TEST=None

Committed: https://crrev.com/a9960587c8b51dd77b01bc3275feb6a22ba4f363
Cr-Commit-Position: refs/heads/master@{#294050}

[pkotwicz, 2014-09-09 00:38:00]

pkotwicz@chromium.org changed reviewers:
+ sadrul@chromium.org

[pkotwicz, 2014-09-09 00:38:00]

Sadrul PTAL

This CL does not depend on https://codereview.chromium.org/546123002/

The CL fixes a crash which is easy to reproduce when
https://codereview.chromium.org/546123002/ lands (or possible to reproduce if
you are fast enough on ToT)

[sadrul, 2014-09-09 14:40:18]

Where does the crash happen?

[pkotwicz, 2014-09-09 17:30:05]

The crash occurs in RestoreWindowState() when window->layer()->SetOpacity(1.0f)
is called (because setting the opacity completes the close animation)

Repro steps for crash on ToT:
1) Extend the duration of the close window animation
2) Close a window
3) Scroll through the windows and select a different window

I think that this fix is the right fix (and that completing/aborting animations
when WindowOverviewModeImpl is destroyed is the wrong fix). Once
https://codereview.chromium.org/546123002/ lands, if no activity is selected and
overview mode is exited, the topmost activity is selected prior to overview mode
being exited. The selected activity could be the activity which is closing. This
would also cause a crash.

[sadrul, 2014-09-09 19:04:31]

Thanks for the explanation. LGTM

[pkotwicz, 2014-09-09 21:14:08]

pkotwicz@chromium.org changed reviewers:
+ oshima@chromium.org

[pkotwicz, 2014-09-09 21:14:09]

oshima for OWNERS

[oshima, 2014-09-09 21:47:02]

lgtm

[pkotwicz, 2014-09-09 22:51:43]

The CQ bit was checked by pkotwicz@chromium.org

[commit-bot: I haz the power, 2014-09-09 23:06:08]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/pkotwicz@chromium.org/555463003/1

[commit-bot: I haz the power, 2014-09-10 00:29:34]

Committed patchset #1 (id:1) as 60b1268475e0b3af240e71af753c16c92c279902

[commit-bot: I haz the power, 2014-09-10 03:56:57]

Patchset 1 (id:??) landed as
https://crrev.com/a9960587c8b51dd77b01bc3275feb6a22ba4f363
Cr-Commit-Position: refs/heads/master@{#294050}