Oilpan: Move Interpolation's hierarchy to oilpan's heap

This CL moves Interpolation's hierarchy and InterpolationRecord to oilpan's heap. I'll move other Interpolation objects in a follow-up CL.

BUG=341032
NOTRY=true

Review URL: https://codereview.chromium.org/210783002

git-svn-id: svn://svn.chromium.org/blink/trunk@169919 bbb929c8-8fbe-4397-9dbb-9b2b20218538