Add benchmark for investigating memory leaks over desktop sites

This is a new version of the benchmark used to find memory leaks in the
browser process.

The browser process stay alive for the whole duration of the benchmark.
A memory dump using memory-infra is periodically taken.
An external diff tool is used to find remaining objects allocated between
two memory dumps.

see:
  https://docs.google.com/a/google.com/document/d/1ULZRYBElYmBDGswF3f4yYpl77SD9sa0RgFNfl1FueWU/edit?usp=sharing
  https://codereview.chromium.org/2906113002/

CC: erikchen@chromium.org
R: perezju@chromium.org, primiano@chromium.org
Bug: 705656
Change-Id: I697892a6df881d19e3aace5a44e8a395717767c0
Reviewed-on: https://chromium-review.googlesource.com/530527
Reviewed-by: Erik Chen <erikchen@chromium.org>
Reviewed-by: Ned Nguyen <nednguyen@google.com>
Commit-Queue: Etienne Bergeron <etienneb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#478760}
2 files changed