Merge "API for querying/revoking current NotificationAssistant"

diff --cc api/system-current.txt
Simple merge

diff --cc core/java/android/app/INotificationManager.aidl
Simple merge

diff --cc core/java/android/app/NotificationManager.java
Simple merge

diff --cc services/core/java/com/android/server/notification/NotificationManagerService.java
Simple merge

diff --cc services/tests/uiservicestests/src/com/android/server/notification/NotificationManagerServiceTest.java
Simple merge