Check if keepalive is enabled before releasing sessions in DDSM.release

If keepalive is disabled the existing code over-eagerly releases
DrmSession instances. This is arguably OK since a (Default)DrmSession
should be released before its (Default)Manager is released
(since the underlying MediaDrm instance might be released when the
manager is released). And if all sessions are released before the
manager is released then `sessions` is empty, so the loop is a no-op.

Issue: #8576
#minor-release
PiperOrigin-RevId: 356955308

RELEASENOTES.md

@@ -25,6 +25,9 @@
         ([#8523](https://github.com/google/ExoPlayer/issues/8523)).
     *   Propagate DRM configuration when creating media sources for ad content
         ([#8568](https://github.com/google/ExoPlayer/issues/8568)).
+    *   Only release 'keepalive' references to `DrmSession` in
+        `DefaultDrmSessionManager#release()` if keepalive is enabled
+        ([#8576](https://github.com/google/ExoPlayer/issues/8576)).
 *   Remove deprecated symbols:
     *   Remove `Player.DefaultEventListener`. Use `Player.EventListener`
         instead.

library/core/src/main/java/com/google/android/exoplayer2/drm/DefaultDrmSessionManager.java

@@ -457,12 +457,14 @@ public final void release() {
     if (--prepareCallsCount != 0) {
       return;
     }
-    // Make a local copy, because sessions are removed from this.sessions during release (via
-    // callback).
-    List<DefaultDrmSession> sessions = new ArrayList<>(this.sessions);
-    for (int i = 0; i < sessions.size(); i++) {
-      // Release all the keepalive acquisitions.
-      sessions.get(i).release(/* eventDispatcher= */ null);
+    // Release all keepalive acquisitions if keepalive is enabled.
+    if (sessionKeepaliveMs != C.TIME_UNSET) {
+      // Make a local copy, because sessions are removed from this.sessions during release (via
+      // callback).
+      List<DefaultDrmSession> sessions = new ArrayList<>(this.sessions);
+      for (int i = 0; i < sessions.size(); i++) {
+        sessions.get(i).release(/* eventDispatcher= */ null);
+      }
     }
     Assertions.checkNotNull(exoMediaDrm).release();
     exoMediaDrm = null;

library/core/src/test/java/com/google/android/exoplayer2/drm/DefaultDrmSessionManagerTest.java

@@ -147,6 +147,32 @@ public void managerRelease_allKeepaliveSessionsImmediatelyReleased() throws Exce
     assertThat(drmSession.getState()).isEqualTo(DrmSession.STATE_RELEASED);
   }
 
+  @Test(timeout = 10_000)
+  public void managerRelease_keepaliveDisabled_doesntReleaseAnySessions() throws Exception {
+    FakeExoMediaDrm.LicenseServer licenseServer =
+        FakeExoMediaDrm.LicenseServer.allowingSchemeDatas(DRM_SCHEME_DATAS);
+    DrmSessionManager drmSessionManager =
+        new DefaultDrmSessionManager.Builder()
+            .setUuidAndExoMediaDrmProvider(DRM_SCHEME_UUID, uuid -> new FakeExoMediaDrm())
+            .setSessionKeepaliveMs(C.TIME_UNSET)
+            .build(/* mediaDrmCallback= */ licenseServer);
+
+    drmSessionManager.prepare();
+    DrmSession drmSession =
+        checkNotNull(
+            drmSessionManager.acquireSession(
+                /* playbackLooper= */ checkNotNull(Looper.myLooper()),
+                /* eventDispatcher= */ null,
+                FORMAT_WITH_DRM_INIT_DATA));
+    waitForOpenedWithKeys(drmSession);
+    assertThat(drmSession.getState()).isEqualTo(DrmSession.STATE_OPENED_WITH_KEYS);
+
+    // Release the manager, the session should still be open (though it's unusable because
+    // the underlying ExoMediaDrm is released).
+    drmSessionManager.release();
+    assertThat(drmSession.getState()).isEqualTo(DrmSession.STATE_OPENED_WITH_KEYS);
+  }
+
   @Test(timeout = 10_000)
   public void maxConcurrentSessionsExceeded_allKeepAliveSessionsEagerlyReleased() throws Exception {
     ImmutableList<DrmInitData.SchemeData> secondSchemeDatas =