This CL allows the sweeper to free up all memory >= free list item size (3 words). This may reduce memory consumption (especially in map space), but may be worse for allocation order as soon as we start using the tiny category.

This CL is just a first step in the right direction. A follow up CL will add customizable free list categories for each old space.

BUG=chromium:587026
LOG=n

Review URL: https://codereview.chromium.org/1774953003

Cr-Commit-Position: refs/heads/master@{#34612}