The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a0abfdfa0a7131d8dc12f7baf3cc4d76e4e5ea71

commit a0abfdfa0a7131d8dc12f7baf3cc4d76e4e5ea71
Author: perezju <perezju@chromium.org>
Date: Wed Jun 22 12:58:48 2016

Revert of [tools/perf] Keep both browsers open from the start of dual browser test (patchset #1 id:1 of https://codereview.chromium.org/2073713003/ )

Reason for revert:
Broke WPR on the benchmark

Original issue's description:
> [tools/perf] Keep both browsers open from the start of dual browser test
>
> At the start of the story set, open the browsers associated with all
> stories. This makes sure that, when taking memory dumps, we always get
> a dump for all browsers all the time.
>
> BUG= 616043 
>
> Committed: https://crrev.com/f41edc4cf5d1b086ad00d70bf9fcb51d3fe9183e
> Cr-Commit-Position: refs/heads/master@{#400667}

TBR=nednguyen@google.com,primiano@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG= 616043 

Review-Url: https://codereview.chromium.org/2084393002
Cr-Commit-Position: refs/heads/master@{#401264}

[modify] https://crrev.com/a0abfdfa0a7131d8dc12f7baf3cc4d76e4e5ea71/tools/perf/page_sets/dual_browser_story.py

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9a647d91e3999a0ba99963eefd6ce7460483116f

commit 9a647d91e3999a0ba99963eefd6ce7460483116f
Author: perezju <perezju@chromium.org>
Date: Thu Jun 23 14:04:29 2016

[tools/perf] Keep both browsers open for the whole of the dual browser test

Ensure that all browsers needed for the story set remain open for the whole
duration of the test. This makes sure that, when taking memory dumps, we
always get a dump for all browsers all the time.

Previous attempt from https://codereview.chromium.org/2073713003/ did not
work because the browsers need to be created *after* WPR has been started.

BUG= 616043 

Review-Url: https://codereview.chromium.org/2097493002
Cr-Commit-Position: refs/heads/master@{#401598}

[modify] https://crrev.com/9a647d91e3999a0ba99963eefd6ce7460483116f/tools/perf/page_sets/dual_browser_story.py

The fix landed in #2, although the test is still sometimes failing for some other reasons.