Add keyboard shortcuts for next/previous pane on Chrome OS, and fix

alphabetization. Note that the F1 key is the "Back" key on Chrome OS,
and F2 is "Forwards".

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/2878059

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@53827 0039d316-1c4b-4281-b951-d872f2087c98