DevTools: Use v8::Value::IsArgumentsObject via InjectedScriptHost

R=yurys@chromium.org, yurys

Review URL: https://codereview.chromium.org/502003002

git-svn-id: svn://svn.chromium.org/blink/trunk@180976 bbb929c8-8fbe-4397-9dbb-9b2b20218538