Avoid changing enabled features while the browser is already running.

Avoid changing enabled features while the browser is already running.

Changing enabled features while the browser is already running is
inherently racey - the race is between the thread that changes the
features (e.g. by test calling one of
base::test::ScopedFeatureList::Init...  methods on the main thread) and
the thread that tries to read currently enabled features (e.g. by
product code trying to see on the IO thread which features are enabled).

BUG=722409
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_site_isolation

[Łukasz Anforowicz, 2017-05-15 19:57:41]

Description was changed from

==========
Avoid changing enabled features while the browser is already running.

Changing enabled features while the browser is already running is
inherently racey - the race is between the thread that changes the
features (e.g. by test calling one of
base::test::ScopedFeatureList::Init...  methods on the main thread) and
the thread that tries to read currently enabled features (e.g. by
product code trying to see on the IO thread which features are enabled).

BUG=722409
==========

to

==========
Avoid changing enabled features while the browser is already running.

Changing enabled features while the browser is already running is
inherently racey - the race is between the thread that changes the
features (e.g. by test calling one of
base::test::ScopedFeatureList::Init...  methods on the main thread) and
the thread that tries to read currently enabled features (e.g. by
product code trying to see on the IO thread which features are enabled).

BUG=722409
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_site_isolation
==========

[Łukasz Anforowicz, 2017-05-16 00:00:30]

The CQ bit was checked by lukasza@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-05-16 00:01:42]

Dry run: CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-05-16 01:12:11]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-05-16 01:12:12]

Dry run: Try jobs failed on following builders:
  linux_chromium_rel_ng on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)