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I don't know what has caused the recent regression, but this fixes it. The position of the close button is not consistent between windows and mac, I chose to follow mac.

BUG=none

Review URL: https://codereview.chromium.org/11034002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@162306 0039d316-1c4b-4281-b951-d872f2087c98