Delete ad-hoc console implementation in HeapSnapshotWorker

Now that we have native console for dedicated workers there is no need to keep this custom implementation.

BUG=None
R=vsevik@chromium.org

Review URL: https://codereview.chromium.org/23726010

git-svn-id: svn://svn.chromium.org/blink/trunk@157065 bbb929c8-8fbe-4397-9dbb-9b2b20218538