Set uber page's header z-index to be higher than any in network list.
Set uber page's header z-index to be higher than any in network list.

BUG=118117
TEST=Select network in list, scroll page down. Selected network list item should go below header.


Review URL: http://codereview.chromium.org/9705107

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@127472 0039d316-1c4b-4281-b951-d872f2087c98

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