Add @IntDef for flags sent along with volume change

Bug: 173657280
Test: build
Change-Id: Ibb0ea7fe4a33e1498675fc2586960dec2579bea2

media/java/android/media/AudioManager.java

@@ -567,6 +567,25 @@ public class AudioManager {
     @SystemApi(client = SystemApi.Client.MODULE_LIBRARIES)
     public static final int FLAG_FROM_KEY = 1 << 12;
 
+    /** @hide */
+    @IntDef(flag = false, prefix = "FLAG", value = {
+            FLAG_SHOW_UI,
+            FLAG_ALLOW_RINGER_MODES,
+            FLAG_PLAY_SOUND,
+            FLAG_REMOVE_SOUND_AND_VIBRATE,
+            FLAG_VIBRATE,
+            FLAG_FIXED_VOLUME,
+            FLAG_BLUETOOTH_ABS_VOLUME,
+            FLAG_SHOW_SILENT_HINT,
+            FLAG_HDMI_SYSTEM_AUDIO_VOLUME,
+            FLAG_ACTIVE_MEDIA_ONLY,
+            FLAG_SHOW_UI_WARNINGS,
+            FLAG_SHOW_VIBRATE_HINT,
+            FLAG_FROM_KEY,
+    })
+    @Retention(RetentionPolicy.SOURCE)
+    public @interface Flags {}
+
     // The iterator of TreeMap#entrySet() returns the entries in ascending key order.
     private static final TreeMap<Integer, String> FLAG_NAMES = new TreeMap<>();
 

media/java/android/media/session/MediaSessionManager.java

@@ -1127,9 +1127,10 @@ public final class MediaSessionManager {
          * toast showing the volume should be shown.
          *
          * @param sessionToken the remote media session token
-         * @param flags extra information about how to handle the volume change
+         * @param flags flags containing extra action or information regarding the volume change
          */
-        void onVolumeChanged(@NonNull MediaSession.Token sessionToken, int flags);
+        void onVolumeChanged(@NonNull MediaSession.Token sessionToken,
+                @AudioManager.Flags int flags);
 
         /**
          * Called when the default remote session is changed where the default remote session