[Android O] Only delete legacy notification channels on upgrade

[Android O] Only delete legacy notification channels on upgrade

- Now instead of deleting all channels on upgrade, we only delete
those we know to be legacy channels.

- This fixes a crash where we tried to delete the default channel
created by Android causing an IllegalArgumentException.

BUG=710843
Review-Url: https://codereview.chromium.org/2832493002
Cr-Commit-Position: refs/heads/master@{#466352}
(cherry picked from commit e0bb8b3085974f05fcb8c2a8f65a8585d749264f)

Review-Url: https://codereview.chromium.org/2829263002 .
Cr-Commit-Position: refs/branch-heads/3071@{#121}
Cr-Branched-From: a106f0abbf69dad349d4aaf4bcc4f5d376dd2377-refs/heads/master@{#464641}
Committed: https://chromium.googlesource.com/chromium/src/+/5f662891d23246fb57e349185b57cfa663a9db6b

[awdf, 2017-04-21 17:01:05]

Description was changed from

==========
[Android O] Only delete legacy notification channels on upgrade

- Now instead of deleting all channels on upgrade, we only delete
those we know to be legacy channels.

- This fixes a crash where we tried to delete the default channel
created by Android causing an IllegalArgumentException.

BUG=710843

Review-Url: https://codereview.chromium.org/2832493002
Cr-Commit-Position: refs/heads/master@{#466352}
(cherry picked from commit e0bb8b3085974f05fcb8c2a8f65a8585d749264f)
==========

to

==========
[Android O] Only delete legacy notification channels on upgrade

- Now instead of deleting all channels on upgrade, we only delete
those we know to be legacy channels.

- This fixes a crash where we tried to delete the default channel
created by Android causing an IllegalArgumentException.

BUG=710843

Review-Url: https://codereview.chromium.org/2832493002
Cr-Commit-Position: refs/heads/master@{#466352}
(cherry picked from commit e0bb8b3085974f05fcb8c2a8f65a8585d749264f)

Review-Url: https://codereview.chromium.org/2829263002 .
Cr-Commit-Position: refs/branch-heads/3071@{#121}
Cr-Branched-From:
a106f0abbf69dad349d4aaf4bcc4f5d376dd2377-refs/heads/master@{#464641}
Committed:
https://chromium.googlesource.com/chromium/src/+/5f662891d23246fb57e349185b57...
==========

[awdf, 2017-04-21 17:01:06]

Committed patchset #1 (id:1) manually as
5f662891d23246fb57e349185b57cfa663a9db6b.