[heap profiler] Use proper memory ordering in lock-free hash set

The load opererations over bucket linked list access must be marked
acquire to make sure the proper pointer to the next bucket is read.

BUG=958404

Change-Id: I32d17fbb53847d441909f69fbe4c32092e2db53a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1594164
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Commit-Queue: Alexei Filippov <alph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#657013}
2 files changed