[Android O] Add SystemNotification.ChannelBlocked histogram

[Android O] Add SystemNotification.ChannelBlocked histogram

- Added a new histogram for notifications that were already being
logged via NotificationUmaTracker.

- Now, if notifications are enabled at the app level but blocked at the
channel level, they will be counted in this histogram, instead of the
SystemNotification.Shown histogram.

- If notifications are blocked at the app level they will still be
counted in SystemNotification.Blocked, regardless of channel status.

TBR=dtrainor@chromium.org

BUG=706813
Review-Url: https://codereview.chromium.org/2834633002
Cr-Commit-Position: refs/heads/master@{#466424}
(cherry picked from commit d0ba3b6e3f693d2a11992a48dc28508bbfc89731)

Review-Url: https://codereview.chromium.org/2837283002 .
Cr-Commit-Position: refs/branch-heads/3071@{#197}
Cr-Branched-From: a106f0abbf69dad349d4aaf4bcc4f5d376dd2377-refs/heads/master@{#464641}
Committed: https://chromium.googlesource.com/chromium/src/+/ab21f85201dc5947c009f97c6d0caf505f2be897

[awdf, 2017-04-25 09:48:45]

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

[commit-bot: I haz the power, 2017-04-25 09:49:06]

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, 2017-04-25 09:49:07]

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

[commit-bot: I haz the power, 2017-04-25 09:49:09]

Dry run: CLs for remote refs other than refs/heads/master must contain
NOTRY=true and NOPRESUBMIT=true in order for the CQ to process them

[awdf, 2017-04-25 09:50:32]

Description was changed from

==========
[Android O] Add SystemNotification.ChannelBlocked histogram

- Added a new histogram for notifications that were already being
logged via NotificationUmaTracker.

- Now, if notifications are enabled at the app level but blocked at the
channel level, they will be counted in this histogram, instead of the
SystemNotification.Shown histogram.

- If notifications are blocked at the app level they will still be
counted in SystemNotification.Blocked, regardless of channel status.

TBR=dtrainor@chromium.org

BUG=706813

Review-Url: https://codereview.chromium.org/2834633002
Cr-Commit-Position: refs/heads/master@{#466424}
(cherry picked from commit d0ba3b6e3f693d2a11992a48dc28508bbfc89731)
==========

to

==========
[Android O] Add SystemNotification.ChannelBlocked histogram

- Added a new histogram for notifications that were already being
logged via NotificationUmaTracker.

- Now, if notifications are enabled at the app level but blocked at the
channel level, they will be counted in this histogram, instead of the
SystemNotification.Shown histogram.

- If notifications are blocked at the app level they will still be
counted in SystemNotification.Blocked, regardless of channel status.

TBR=dtrainor@chromium.org

BUG=706813

Review-Url: https://codereview.chromium.org/2834633002
Cr-Commit-Position: refs/heads/master@{#466424}
(cherry picked from commit d0ba3b6e3f693d2a11992a48dc28508bbfc89731)

Review-Url: https://codereview.chromium.org/2837283002 .
Cr-Commit-Position: refs/branch-heads/3071@{#197}
Cr-Branched-From:
a106f0abbf69dad349d4aaf4bcc4f5d376dd2377-refs/heads/master@{#464641}
Committed:
https://chromium.googlesource.com/chromium/src/+/ab21f85201dc5947c009f97c6d0c...
==========

[awdf, 2017-04-25 09:50:34]

Committed patchset #1 (id:1) manually as
ab21f85201dc5947c009f97c6d0caf505f2be897.