Makes enter/shift-enter find next/previous on Mac.
Makes enter/shift-enter find next/previous on Mac.

BUG=htp://crbug.com/14890
TEST=Cmd-F to find in page.  Type a word into the box,
then ensure that pressing Enter finds the next instance,
Shift-Enter finds the previous instance.
Review URL: http://codereview.chromium.org/149100

git-svn-id: http://src.chromium.org/svn/trunk/src@20996 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: d50b3ee9364a88dcc53389b12e5413b0cccef243
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