GitLab

* Create an enum PromoType and a data member promo_type_ of NotificationPromo.
* InitFromJson, InitFromPrefs, HandleClosed and HandleViewed all take a PromoType now.
* HandleClosed and HandleViewed are static.
* Add an anon function PromoTypeToString for conversion from PromoType to string.
* Improve unit tests TestViewed() and TestClosed().

BUG=123061
TEST=unit tests. Manual.

Review URL: https://chromiumcodereview.appspot.com/10836099

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@150235 0039d316-1c4b-4281-b951-d872f2087c98