Mac: Add a few more keyboard shortcuts to tabpose.
Mac: Add a few more keyboard shortcuts to tabpose.

* shift / tab-shift cycle through all open tabs
* arrow keys move selection up, down, left, right
* cmd-1-8 selects tab 1-8 and exits tabpose, cmd-9 selects last tab and exits tabpose
* cmd-ctrl-t exits tabpose

BUG=50307,55530
TEST=try it

Review URL: http://codereview.chromium.org/3389010

git-svn-id: http://src.chromium.org/svn/trunk/src@59703 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 47751116a01d1abe7a414e2821c7a6aa7a44e315
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser