Only allow notifications to grow in size (as the content size is determined).  Mac OS sometimes rapidly reports two alternating sizes, causing the animations to seize up and flicker.
Only allow notifications to grow in size (as the content size is determined).  Mac OS sometimes rapidly reports two alternating sizes, causing the animations to seize up and flicker.

BUG=38083
TEST=visit http://www/~johnnyg/38083.html, or otherwise invoke the javascript in the bug.  there should be no animation problems.

Review URL: http://codereview.chromium.org/1589020

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@43857 0039d316-1c4b-4281-b951-d872f2087c98

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