Fix crash in device_sensors.

Fix crash in device_sensors.

If a consumer type is not supported, it is not added to
consumers_bitmask_ in AddConsumer. But in RemoveConsumer it is xored
into the mask, because fetcher_->Stop normally returns true for valid
consumer types; then this mask is passed into fetcher_->Fetch, and
e.g. on mac the fetcher crashes.

BUG=

Committed: https://crrev.com/9d8539f53682e5a08a3dfa9524f399aa2406a528
Cr-Commit-Position: refs/heads/master@{#357103}

[Alexander Semashko, 2015-10-27 15:14:35]

ahest@yandex-team.ru changed reviewers:
+ leandrogracia@chromium.org

[Alexander Semashko, 2015-10-30 10:22:19]

Description was changed from

==========
Fix crash in device_sensors.

If a consumer type is not supported, it is not added to
consumers_bitmask_ in AddConsumer. But in RemoveConsumer it is xored
into the mask, because fetcher_->Stop normally returns true for valid
consumer types; then this mask is passed into fetcher_->Fetch, and
e.g. on mac the fetcher crashes.

BUG=
==========

to

==========
Fix crash in device_sensors.

If a consumer type is not supported, it is not added to
consumers_bitmask_ in AddConsumer. But in RemoveConsumer it is xored
into the mask, because fetcher_->Stop normally returns true for valid
consumer types; then this mask is passed into fetcher_->Fetch, and
e.g. on mac the fetcher crashes.

BUG=
==========

[Alexander Semashko, 2015-10-30 10:22:19]

ahest@yandex-team.ru changed reviewers:
+ hans@chromium.org

[Alexander Semashko, 2015-10-30 10:22:45]

hans, can you take a look please?

[timvolodine, 2015-10-30 13:27:05]

On 2015/10/30 10:22:45, ahest wrote:
> hans, can you take a look please?

hans and leandro are on a different team since a while ago, we should probably
update the owners.

Yes, good catch, thanks for fixing this! LGTM.

[Alexander Semashko, 2015-10-30 13:40:55]

The CQ bit was checked by ahest@yandex-team.ru

[commit-bot: I haz the power, 2015-10-30 13:41:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1428533003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1428533003/1

[commit-bot: I haz the power, 2015-10-30 14:48:45]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-30 14:49:28]

Patchset 1 (id:??) landed as
https://crrev.com/9d8539f53682e5a08a3dfa9524f399aa2406a528
Cr-Commit-Position: refs/heads/master@{#357103}