TV PIP: Fix broken TV PIP

Bug: 37249867
Test: Manual test (checked that the notification UI is shown when the
    PIP starts, and dismissed when the PIP is closed. The 'DETAILS' and
    the 'DISMISS' button in the notification also worked.)
Change-Id: I12e385b51f834991a0115ce5ba7dd98180577adb
diff --git a/proto/src/system_messages.proto b/proto/src/system_messages.proto
index 53b3fe9..2f6b7e6 100644
--- a/proto/src/system_messages.proto
+++ b/proto/src/system_messages.proto
@@ -212,6 +212,10 @@
     // Package: com.android.systemui
     NOTE_LOGOUT_USER = 1011;
 
+    // Notify the user that a TV PIP is running.
+    // Package: com.android.systemui
+    NOTE_TV_PIP = 1100;
+
     // Communicate to the user about remote bugreports.
     // Package: android
     NOTE_REMOTE_BUGREPORT = 678432343;