Add support for Page.getResourceTree

Unfortunately we don't yet have a way to walk into
imports, so this only is the first-level of the
source tree, but this is a huge step forward.

You can now click to set breakpoints, however
setting breakpoints crashes sky.

I had to fix Console.log to flush stdout
so that I could actually debug my timing-out test.

Also had to fix Chai to dump differences for deepEqual.

R=esprehn@chromium.org, abarth@chromium.org, esprhen@chromium.org

Review URL: https://codereview.chromium.org/732413004