Updates MediaDrm developer docs

Distinguish between secure stops and secure stop ids

bug:76449152
Change-Id: I4ff26b645bd4a156738ba358de598e2ccb1b0584

media/java/android/media/MediaDrm.java

@@ -991,6 +991,9 @@ public final class MediaDrm implements AutoCloseable {
      * active. The license server returns a secure stop release response
      * message to the app which then deletes the secure stop from persistent
      * memory using {@link #releaseSecureStops}.
+     * <p>
+     * Each secure stop has a unique ID that can be used to identify it during
+     * enumeration, access and removal.
      * @return a list of all secure stops from secure persistent memory
      */
     @NonNull
@@ -998,6 +1001,8 @@ public final class MediaDrm implements AutoCloseable {
 
     /**
      * Return a list of all secure stop IDs currently in persistent memory.
+     * The secure stop ID can be used to access or remove the corresponding
+     * secure stop.
      *
      * @return a list of secure stop IDs
      */
@@ -1006,6 +1011,7 @@ public final class MediaDrm implements AutoCloseable {
 
     /**
      * Access a specific secure stop given its secure stop ID.
+     * Each secure stop has a unique ID.
      *
      * @param ssid the ID of the secure stop to return
      * @return the secure stop identified by ssid