Support the numpad keys on the calculator app

BUG=155449
TEST=manually
R=dharcourt@chromium.org

Review URL: https://codereview.chromium.org/149433002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248981 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248981