Add basic console support to Sky's inspector.

I think longer-term we want to instead fork
InjectedScriptSource.js:
http://blink.lc/blink/tree/Source/core/inspector/InjectedScriptSource.js
since a ton of the "remote object" logic could be shared
between Blink and Sky here.

Since we're trying to talk exactly Chrome's inspector
protocol we should start from the Blink JS as much as possible.

That said, this is enough to get the Chrome devtools
inspector to talk to sky and have the console handle
basic commands!

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/674823003