Fix crashes wrt to maximize button and touch

Fixes crashes wrt to the maximize button when:
- A user hovers the minimize button with the mouse then taps the snap left / snap right button
- When the MaximizeBubbleFrameState computed by GetMaximizeBubbleFrameState() changes while the maximize button help bubble is visible due to the work area bounds changing (See comment #6 in bug)

BUG=342867
TEST=FrameMaximizeButtonTest.MaximizeBubbleMouseHoverAndTouch

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=251206

[pkotwicz, 2014-02-13 02:19:14]

Stefan, can you please take a look?

[Mr4D (OOO till 08-26), 2014-02-13 15:14:32]

Please see comment

https://codereview.chromium.org/160493004/diff/280001/ash/wm/caption_buttons/...
File ash/wm/caption_buttons/frame_maximize_button.cc (right):

https://codereview.chromium.org/160493004/diff/280001/ash/wm/caption_buttons/...
ash/wm/caption_buttons/frame_maximize_button.cc:234:
wm::GetWindowState(window)->RemoveObserver(this);
Shouldn't this be an AddObserver?

[pkotwicz, 2014-02-13 15:57:19]

Stefan, can you please take another look?

[Mr4D (OOO till 08-26), 2014-02-13 16:32:45]

lgtm

[pkotwicz, 2014-02-13 19:26:27]

The CQ bit was checked by pkotwicz@chromium.org

[commit-bot: I haz the power, 2014-02-13 19:29:12]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/pkotwicz@chromium.org/160493004/340001

[commit-bot: I haz the power, 2014-02-13 20:04:46]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/pkotwicz@chromium.org/160493004/340001

[commit-bot: I haz the power, 2014-02-14 00:35:29]

Change committed as 251206