Long time ago there were two passes over heap. One was counting
objects and edge and another was filling them. Since then we have
just a single pass, but the filler object is still there.

Remove it for the sake of layering simplicity.

Reviewed-on: https://chromium-review.googlesource.com/1244380
Commit-Queue: Alexei Filippov <alph@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56246}

TBR=ulan@chromium.org

Change-Id: Ie155a79f7aaf9b2612ae89f67b793ba813c364c9
Reviewed-on: https://chromium-review.googlesource.com/c/1261882Reviewed-by: Alexei Filippov <alph@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Alexei Filippov <alph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56387}