MediaSession: Fix the API documentation inconsistency

Bug: 24974209
Change-Id: I0f8816ec491ecfdb405dc98fb0837b5720d06c38
diff --git a/v4/java/android/support/v4/media/session/MediaSessionCompat.java b/v4/java/android/support/v4/media/session/MediaSessionCompat.java
index 69a4180..d98b22e 100644
--- a/v4/java/android/support/v4/media/session/MediaSessionCompat.java
+++ b/v4/java/android/support/v4/media/session/MediaSessionCompat.java
@@ -288,8 +288,8 @@
      * <p>
      * On platforms earlier than
      * {@link android.os.Build.VERSION_CODES#LOLLIPOP},
-     * {@link #setMediaButtonReceiver(PendingIntent)} must be called before
-     * setting this to true.
+     * a media button event receiver should be set via the constructor to
+     * receive media button events.
      *
      * @param active Whether this session is active or not.
      */