Remove a couple more core/ header includes from v8_inspector

Removed all uses of Frame in InspectorTraceEvents
in the process, since none of them actually
needed a Frame (since each sky instance only
has one frame).

I've just been burning down the list of core
includes using:
grep "#include" sky/engine/v8_inspector/* -h | sort | uniq | sort | grep core

TBR=yurys@chromium.org
BUG=435243

Review URL: https://codereview.chromium.org/771323002