Adjust the border-color and box-shadow on container elements to match the new...

Adjust the border-color and box-shadow on container elements to match the new f1f1f1 background-color. See #25858, props melchoyce.
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git-svn-id: https://core.svn.wordpress.org/trunk@26727 1a063a9b-81f0-0310-95a4-ce76da25c4cd