Stop using a placeholder image for dev mode highlighting.

Start using assets from the designer.

BUG=328441
R=asargent@chromium.org, oshima@chromium.org

Review URL: https://codereview.chromium.org/113573003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241036 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241036