Add devtools resources rules to the GN build.

This should duplicate the devtools resources, with the exception of the "debug" build of devtools.

R=apavlov@chromium.org, jamesr@chromium.org

Review URL: https://codereview.chromium.org/302093008

git-svn-id: svn://svn.chromium.org/blink/trunk@175501 bbb929c8-8fbe-4397-9dbb-9b2b20218538