[Mac] Change the style of the infobar buttons.
[Mac] Change the style of the infobar buttons.

XIB changes:
* Change both the ok and cancel buttons to use "Rounded Texture" style instead
  of "Round Rect".
* Since this is a larger button style, move the baseline of the buttons up 3px.
* Move the baseline of the close button up 1px.

BUG=none
TEST=visual


Review URL: http://codereview.chromium.org/7108079

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@88885 0039d316-1c4b-4281-b951-d872f2087c98

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