heap: Remove support for eager tracing

Oilpan has moved away from CRTP to a dynamic visitor interface some time ago
now. Since there is no real chance for inlining visitation methods anymore we
can also remove eager tracing. The worklist uses segments which means that there
is likely also only few allocations required.

Estimates show that this improves performance (throughput) about ~13%.

Change-Id: I0301d3feacaf1248a6ed87fa9dbd7425ca46d301
Bug: 933333
Reviewed-on: https://chromium-review.googlesource.com/c/1477833
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#636027}
9 files changed