GitLab

This CL renames these classes:
- MessageCenterNotificationManager -> NotificationUIManagerImpl
- MessageCenterNotificationManagerTest -> NotificationUIManagerTest
- MessageCenterNotificationsTest -> NotificationUIManagerBrowserTest
- MessageCenterNotificationManagerBrowserTest
    -> NotificationUIManagerInteractiveUITest

MessageCenterNotificationManager was confusing, because this class is
not for CrOS (which has message center) but for Win/Mac/Linux (popup only).

This CL renames this class into NotificationUIManagerImpl, because this is
an implementation of NotificationUIManager. And this also renames the
related test classes accordingly.

Bug: 869278
Test: trybots pass

Change-Id: I296f46d0b8634c95081167d6585f6f42798661f6
Reviewed-on: https://chromium-review.googlesource.com/1158669
Commit-Queue: Yoshiki Iguchi <yoshiki@chromium.org>
Reviewed-by: Evan Stade <estade@chromium.org>
Reviewed-by: Peter Beverloo <peter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#580955}