Add handling end of stream in the ExoplayerCuesDecoder

Empty buffer with flag C.BUFFER_FLAG_END_OF_STREAM is send at the end
of the stream. Handling that flag properly is necessary to make the
ExoplayerCuesDecoder work properly with components like TextRenderer.

PiperOrigin-RevId: 394472642

library/core/src/main/java/com/google/android/exoplayer2/text/ExoplayerCuesDecoder.java

@@ -93,11 +93,15 @@ public final class ExoplayerCuesDecoder implements SubtitleDecoder {
     if (inputBufferState != INPUT_BUFFER_QUEUED || availableOutputBuffers.isEmpty()) {
       return null;
     }
-    SingleEventSubtitle subtitle =
-        new SingleEventSubtitle(
-            inputBuffer.timeUs, cueDecoder.decode(checkNotNull(inputBuffer.data).array()));
     SubtitleOutputBuffer outputBuffer = availableOutputBuffers.removeFirst();
-    outputBuffer.setContent(inputBuffer.timeUs, subtitle, /* subsampleOffsetUs=*/ 0);
+    if (inputBuffer.isEndOfStream()) {
+      outputBuffer.addFlag(C.BUFFER_FLAG_END_OF_STREAM);
+    } else {
+      SingleEventSubtitle subtitle =
+          new SingleEventSubtitle(
+              inputBuffer.timeUs, cueDecoder.decode(checkNotNull(inputBuffer.data).array()));
+      outputBuffer.setContent(inputBuffer.timeUs, subtitle, /* subsampleOffsetUs=*/ 0);
+    }
     inputBuffer.clear();
     inputBufferState = INPUT_BUFFER_AVAILABLE;
     return outputBuffer;

library/core/src/test/java/com/google/android/exoplayer2/text/ExoplayerCuesDecoderTest.java

@@ -19,6 +19,7 @@ import static com.google.common.truth.Truth.assertThat;
 import static org.junit.Assert.assertThrows;
 
 import androidx.test.ext.junit.runners.AndroidJUnit4;
+import com.google.android.exoplayer2.C;
 import com.google.common.collect.ImmutableList;
 import java.util.ArrayList;
 import java.util.List;
@@ -94,6 +95,17 @@ public class ExoplayerCuesDecoderTest {
   }
 
   @Test
+  public void dequeueOutputBuffer_queuedOnEndOfStreamInputBuffer_returnsEndOfStreamOutputBuffer()
+      throws Exception {
+    SubtitleInputBuffer inputBuffer = decoder.dequeueInputBuffer();
+    inputBuffer.setFlags(C.BUFFER_FLAG_END_OF_STREAM);
+    decoder.queueInputBuffer(inputBuffer);
+    SubtitleOutputBuffer outputBuffer = decoder.dequeueOutputBuffer();
+
+    assertThat(outputBuffer.isEndOfStream()).isTrue();
+  }
+
+  @Test
   public void dequeueInputBuffer_withQueuedInput_returnsNull() throws Exception {
     SubtitleInputBuffer inputBuffer = decoder.dequeueInputBuffer();
     writeDataToInputBuffer(inputBuffer, /* timeUs=*/ 1000, ENCODED_CUES);