Add migration from old to new NTP Promo pref structure.

Add migration from old to new NTP Promo pref structure.

The structure of the pref that stores NTP Promos changed when support
was added for storing multiple NTP Promos. This CL adds code to handle
migrating the data from the old structure to the new structure, so that
there is no data loss when users upgrade.

BUG=620554
Committed: https://crrev.com/9d7ff2e8d36006998c5eadbc5f560990de231dcd
Cr-Commit-Position: refs/heads/master@{#402356}

[gchatz, 2016-06-23 00:06:51]

gchatz@chromium.org changed reviewers:
+ rohitrao@chromium.org

[gchatz, 2016-06-27 16:22:37]

On 2016/06/23 00:06:51, gchatz wrote:

ping

[rohitrao (ping after 24h), 2016-06-27 17:04:19]

LGTM

When can we remove this migration code?  In a milestone or two?  Is there a bug
to track that?

https://codereview.chromium.org/2094523002/diff/20001/ios/chrome/browser/noti...
File ios/chrome/browser/notification_promo.cc (right):

https://codereview.chromium.org/2094523002/diff/20001/ios/chrome/browser/noti...
ios/chrome/browser/notification_promo.cc:163: this->MigrateOldPrefs();
Why do you need "this->" ?

https://codereview.chromium.org/2094523002/diff/20001/ios/chrome/browser/noti...
File ios/chrome/browser/notification_promo_unittest.cc (right):

https://codereview.chromium.org/2094523002/diff/20001/ios/chrome/browser/noti...
ios/chrome/browser/notification_promo_unittest.cc:316: // Initialize promo and
verify that its instance variables match the data
Also verify that the old prefs are gone?

[gchatz, 2016-06-27 23:12:22]

Filed a bug for removing the migration code, and added TODOS for it.

https://codereview.chromium.org/2094523002/diff/20001/ios/chrome/browser/noti...
File ios/chrome/browser/notification_promo.cc (right):

https://codereview.chromium.org/2094523002/diff/20001/ios/chrome/browser/noti...
ios/chrome/browser/notification_promo.cc:163: this->MigrateOldPrefs();
On 2016/06/27 17:04:19, rohitrao wrote:
> Why do you need "this->" ?

Done.

https://codereview.chromium.org/2094523002/diff/20001/ios/chrome/browser/noti...
File ios/chrome/browser/notification_promo_unittest.cc (right):

https://codereview.chromium.org/2094523002/diff/20001/ios/chrome/browser/noti...
ios/chrome/browser/notification_promo_unittest.cc:316: // Initialize promo and
verify that its instance variables match the data
On 2016/06/27 17:04:19, rohitrao wrote:
> Also verify that the old prefs are gone?

Added check for this.

[gchatz, 2016-06-27 23:32:56]

The CQ bit was checked by gchatz@chromium.org

[gchatz, 2016-06-27 23:32:56]

The patchset sent to the CQ was uploaded after l-g-t-m from
rohitrao@chromium.org
Link to the patchset: https://codereview.chromium.org/2094523002/#ps40001
(title: "edits")

[commit-bot: I haz the power, 2016-06-27 23:34:12]

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, 2016-06-28 01:06:57]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2016-06-28 01:09:59]

Description was changed from

==========
Add migration from old to new NTP Promo pref structure.

The structure of the pref that stores NTP Promos changed when support
was added for storing multiple NTP Promos. This CL adds code to handle
migrating the data from the old structure to the new structure, so that
there is no data loss when users upgrade.

BUG=620554
==========

to

==========
Add migration from old to new NTP Promo pref structure.

The structure of the pref that stores NTP Promos changed when support
was added for storing multiple NTP Promos. This CL adds code to handle
migrating the data from the old structure to the new structure, so that
there is no data loss when users upgrade.

BUG=620554

Committed: https://crrev.com/9d7ff2e8d36006998c5eadbc5f560990de231dcd
Cr-Commit-Position: refs/heads/master@{#402356}
==========

[commit-bot: I haz the power, 2016-06-28 01:10:01]

Patchset 3 (id:??) landed as
https://crrev.com/9d7ff2e8d36006998c5eadbc5f560990de231dcd
Cr-Commit-Position: refs/heads/master@{#402356}