This is a reland of 86da38fd
Original change's description:
> [heap] minor cleanup in allocation observer code
> 
> Change-Id: If0bec38d41a415e9fbfff57ac891de0461bac13b
> Reviewed-on: https://chromium-review.googlesource.com/668836
> Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> Commit-Queue: Ali Ijaz Sheikh <ofrobots@google.com>
> Cr-Commit-Position: refs/heads/master@{#48046}

Change-Id: If5fd9f7d123a62672d5a4450ddeac5a6e29158b8
Reviewed-on: https://chromium-review.googlesource.com/675423
Commit-Queue: Ali Ijaz Sheikh <ofrobots@google.com>
Reviewed-by: Ali Ijaz Sheikh <ofrobots@google.com>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49786}