Oilpan: Remove GC_INFO_{DEFINE,DECLARE} macros

This CL is a cherry-pick of
[oilpan] Make GC_INFO_{DEFINE,DECLARE} macros NOOP
https://codereview.chromium.org/171843002/

BUG=None

Review URL: https://codereview.chromium.org/169293002

git-svn-id: svn://svn.chromium.org/blink/trunk@167743 bbb929c8-8fbe-4397-9dbb-9b2b20218538