Most callers passed kFinalizeIncrementalMarkingMask, so use that as
a default argument (not using default argument syntax to avoid including
heap.h in cctest.h).

Change-Id: I904f1eb3a0f5fdbe63eab16f6a6f01d04618645d
Reviewed-on: https://chromium-review.googlesource.com/488104Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44950}