DevTools: support targets that don't have Resource agent
DevTools: support targets that don't have Resource agent

We already supported this for dedicated workers, this CL extends this functionality to other types of targets (e.g. standalone v8).

BUG=None

Review URL: https://codereview.chromium.org/1219313002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@198315 bbb929c8-8fbe-4397-9dbb-9b2b20218538

Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk