Oilpan: move Console objects to the oilpan heap.

Turn the ConsoleBase object into a garbage collected object if Oilpan
is enabled, avoiding its ref forwarding to either Console or WorkerConsole.

R=haraken@chromium.org,ager@chromium.org
BUG=340522

Review URL: https://codereview.chromium.org/206093005

git-svn-id: svn://svn.chromium.org/blink/trunk@169670 bbb929c8-8fbe-4397-9dbb-9b2b20218538