Fix the Mac status bubble.

This partially reverts the "cleanup" of r250260. The "cleaner" version is not equivalent if the call to -[NSWindow animations] returns nil.

BUG=none
TEST=no change

Review URL: https://codereview.chromium.org/148113011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251082 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251082