When black allocation is active, all objects allocated in old space are allocated black. Important: With that change, you cannot assume anymore that new objects are white right after their allocation. Currently, black allocation is enabled when incremental marking is started.

This feature can be turned off via flag: --noblack-allocation

BUG=chromium:561449
LOG=n

Review URL: https://codereview.chromium.org/1420423009

Cr-Commit-Position: refs/heads/master@{#34743}