Merge "Document more about volume provider ID."
diff --git a/media/java/android/media/VolumeProvider.java b/media/java/android/media/VolumeProvider.java
index ed272d5..7cf63f4 100644
--- a/media/java/android/media/VolumeProvider.java
+++ b/media/java/android/media/VolumeProvider.java
@@ -89,7 +89,7 @@
      *            this provider.
      * @param maxVolume The maximum allowed volume.
      * @param currentVolume The current volume on the output.
-     * @param volumeControlId The volume control id of this provider.
+     * @param volumeControlId The volume control ID of this provider.
      */
     public VolumeProvider(@ControlType int volumeControl, int maxVolume, int currentVolume,
             @Nullable String volumeControlId) {
@@ -142,10 +142,10 @@
     }
 
     /**
-     * Gets the volume control id. It can be used to identify which volume provider is
+     * Gets the volume control ID. It can be used to identify which volume provider is
      * used by the session.
      *
-     * @return the volume control id or {@code null} if it isn't set.
+     * @return the volume control ID or {@code null} if it isn't set.
      */
     @Nullable
     public final String getVolumeControlId() {
diff --git a/media/java/android/media/session/MediaController.java b/media/java/android/media/session/MediaController.java
index c2f6206..aa57233 100644
--- a/media/java/android/media/session/MediaController.java
+++ b/media/java/android/media/session/MediaController.java
@@ -1056,8 +1056,15 @@
         /**
          * Gets the volume control ID for this session. It can be used to identify which
          * volume provider is used by the session.
+         * <p>
+         * When the session starts to use {@link #PLAYBACK_TYPE_REMOTE remote volume handling},
+         * a volume provider should be set and it may set the volume control ID of the provider
+         * if the session wants to inform which volume provider is used.
+         * It can be {@code null} if the session didn't set the volume control ID or it uses
+         * {@link #PLAYBACK_TYPE_LOCAL local playback}.
+         * </p>
          *
-         * @return the volume control ID for this session or {@code null} if it's local playback
+         * @return the volume control ID for this session or {@code null} if it uses local playback
          * or not set.
          * @see VolumeProvider#getVolumeControlId()
          */