Do not reset period uid when DashMediaSource is released

When the source is prepared again after stop, the period uid
is calculated by subtracting the `firstPeriodId` from the
period uid that is passed in to `createPeriod`. When this
happens after stop, the uid from the old period uid that
is still stored and has the value of the last played uid.

Hence the `firstPeriodId` must not be reset when released.

Issue: google/ExoPlayer#10838
PiperOrigin-RevId: 539028570

RELEASENOTES.md

@@ -87,6 +87,9 @@
 *   Cronet Extension:
 *   RTMP Extension:
 *   DASH Extension:
+    *   Fix a bug where re-preparing a multi-period live Dash media source
+        produced a `IndexOutOfBoundsException`
+        ([#10838](https://github.com/google/ExoPlayer/issues/10838)).
 *   HLS Extension:
 *   Smooth Streaming Extension:
 *   RTSP Extension:

libraries/exoplayer_dash/src/main/java/androidx/media3/exoplayer/dash/DashMediaSource.java

@@ -525,7 +525,7 @@ public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator, long star
     DrmSessionEventListener.EventDispatcher drmEventDispatcher = createDrmEventDispatcher(id);
     DashMediaPeriod mediaPeriod =
         new DashMediaPeriod(
-            firstPeriodId + periodIndex,
+            /* id= */ firstPeriodId + periodIndex,
             manifest,
             baseUrlExclusionList,
             periodIndex,
@@ -573,7 +573,6 @@ protected void releaseSourceInternal() {
     elapsedRealtimeOffsetMs = C.TIME_UNSET;
     staleManifestReloadAttempt = 0;
     expiredManifestPublishTimeUs = C.TIME_UNSET;
-    firstPeriodId = 0;
     periodsById.clear();
     baseUrlExclusionList.reset();
     drmSessionManager.release();