[tools/perf] Keep both browsers open from the start of dual browser test

[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}

[perezju, 2016-06-16 15:54:10]

perezju@chromium.org changed reviewers:
+ nednguyen@google.com, primiano@chromium.org

[nednguyen, 2016-06-16 17:04:12]

lgtm

[Primiano Tucci (use gerrit), 2016-06-17 07:38:45]

lgtm

[perezju, 2016-06-20 12:15:19]

The CQ bit was checked by perezju@chromium.org

[commit-bot: I haz the power, 2016-06-20 12:15:27]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2073713003/1

[commit-bot: I haz the power, 2016-06-20 13:21:22]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-06-20 13:22:45]

Description was changed from

==========
[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
==========

to

==========
[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}
==========

[commit-bot: I haz the power, 2016-06-20 13:22:46]

Patchset 1 (id:??) landed as
https://crrev.com/f41edc4cf5d1b086ad00d70bf9fcb51d3fe9183e
Cr-Commit-Position: refs/heads/master@{#400667}

[perezju, 2016-06-22 12:00:23]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/2084393002/ by perezju@chromium.org.

The reason for reverting is: Broke WPR on the benchmark.