Add check to determine if HidingWindowAnimationObserver is source of crbug.com/338788

Add check to HidingWindowAnimationObserver to determine if a child window of the window animating hidden outliving the window being animated is the source of http://crbug.com/338788

BUG=338788
TEST=None

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=249464

[pkotwicz, 2014-02-05 05:18:47]

Scott, can you please take a look?

I realize this is not what you had in mind. (Though I do not understand what had
in mind) However, I am convinced that this CL will change the signature of the
crash in crbug.com/338788 for all instances (if HidingWindowAnimationObserver is
the source of the crash).

aura::Window::AcquireLayer() is not the source of the crash. As long as the
layer is alive, who owns the layer is irrelevant. e.g. the return value of
aura::Window::layer() is unchanged. We can get into trouble though when
HidingWindowAnimationObserver's destructor deletes the layers that it has
ownership of (because someone may want to access those layers after they were
deleted)

[sky, 2014-02-05 21:38:15]

https://codereview.chromium.org/150573007/diff/30002/ui/views/corewm/window_a...
File ui/views/corewm/window_animations.cc (right):

https://codereview.chromium.org/150573007/diff/30002/ui/views/corewm/window_a...
ui/views/corewm/window_animations.cc:141: CHECK(topmost_window_ ||
observed_.empty());
If observed_ is not empty, is it possible to embed the name of the window so
that it is part of the crash report?

[pkotwicz, 2014-02-05 23:56:33]

Scott, can you please take another look?

[sky, 2014-02-06 00:49:38]

https://codereview.chromium.org/150573007/diff/180001/ui/views/corewm/window_...
File ui/views/corewm/window_animations.cc (right):

https://codereview.chromium.org/150573007/diff/180001/ui/views/corewm/window_...
ui/views/corewm/window_animations.cc:147: CHECK_EQ(0u, observed_.size());
Wouldn't CHECK(false) be clearer here?

[pkotwicz, 2014-02-06 02:24:22]

Scott, can you please take another look?

https://codereview.chromium.org/150573007/diff/180001/ui/views/corewm/window_...
File ui/views/corewm/window_animations.cc (right):

https://codereview.chromium.org/150573007/diff/180001/ui/views/corewm/window_...
ui/views/corewm/window_animations.cc:147: CHECK_EQ(0u, observed_.size());
On 2014/02/06 00:49:38, sky wrote:
> Wouldn't CHECK(false) be clearer here?

Done.

[sky, 2014-02-06 03:24:56]

LGTM

[pkotwicz, 2014-02-06 15:23:33]

The CQ bit was checked by pkotwicz@chromium.org

[commit-bot: I haz the power, 2014-02-06 15:24:49]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/pkotwicz@chromium.org/150573007/250001

[commit-bot: I haz the power, 2014-02-06 18:49:57]

Change committed as 249464