Populate scope sections with variable name/values

Now when debugger is paused scope sections are properly populated with corresponding name:value pairs for all variables.

Eventually InjectedScript may become something like a regular Sky module but at the moment I don't see how to do this gracefully given that it is parametrised by InjectedScriptHost binding. So at the moment I just store it in "injectedScript" property on the global object,

BUG=435243
R=abarth@chromium.org

Review URL: https://codereview.chromium.org/766683005