Zero-initialize persistent heap vector inline backing buffers.
A persistent heap collection object is allocated off-heap,
along with its inlined buffer (if any.)
For heap-allocated backing buffers (inlined in a heap vector or
separate), the Oilpan allocator will provide a zero-initialized
chunk of memory to use. Consequently the invariant initially
holds that unused slots of the backing buffer are all zero initialized
-- something needed for precise tracing during GC marking
To have that invariant hold for the persistent heap vectors also,
we have to explicitly clear out the inline backing buffers on
(off-heap) allocation.
R=haraken
BUG=420515
Review URL: https://codereview.chromium.org/1410223006
Cr-Commit-Position: refs/heads/master@{#356014}
3 files changed
