Mac: Fix corner case of fading out Bookmark bar buttons for no reason
Mac: Fix corner case of fading out Bookmark bar buttons for no reason

The bug report was that you could create bookmark bar items that weren't truncated but still got the fadeout effect we use for truncated bookmark bar items.

The reason this was happening was because our calculation of when Cocoa was going to clip the text was off. Solution: Add a slop value to better match Cocoa.

BUG=53868
TEST=Repro steps in bug.

Review URL: http://codereview.chromium.org/3872004

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@63354 0039d316-1c4b-4281-b951-d872f2087c98

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