Oilpan: Move DocumentMarkerController to the Oilpan heap and use builtin
weak processing for the marker map.

Review URL: https://codereview.chromium.org/288173004

git-svn-id: svn://svn.chromium.org/blink/trunk@174081 bbb929c8-8fbe-4397-9dbb-9b2b20218538