[Panels Win] Support closing panel from taskbar menu.

Crash in bug is because PanelView was not handling the close when it is triggered by taskbar menu, so Panel is never removed from its panel strip, leaving bogus pointers in the panel strip.

BUG=156206
TEST=Close a panel using taskbar menu.

Review URL: https://chromiumcodereview.appspot.com/11195018

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@162552 0039d316-1c4b-4281-b951-d872f2087c98
3 files changed