Skip arbitrary chunks before WAV fmt chunk.

I've seen a sample that has a LIST chunk prior to fmt. It
seems best just to skip all chunks until the format is
located. As per the RIFF spec:

"Programs must expect (and ignore) any unknown chunks
encountered, as with all RIFF forms."

https://www.aelius.com/njh/wavemetatools/doc/riffmci.pdf
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=121682470

library/src/main/java/com/google/android/exoplayer/chunk/ChunkTrackStream.java

@@ -218,12 +218,13 @@ public class ChunkTrackStream implements TrackStream, Loader.Callback {
       mediaChunks.removeFirst();
     }
     BaseMediaChunk currentChunk = mediaChunks.getFirst();
-    Format currentFormat = currentChunk.format;
-    if (downstreamFormat == null || !downstreamFormat.equals(currentFormat)) {
-      eventDispatcher.downstreamFormatChanged(currentFormat, currentChunk.trigger,
+
+    Format format = currentChunk.format;
+    if (!format.equals(downstreamFormat)) {
+      eventDispatcher.downstreamFormatChanged(format, currentChunk.trigger,
           currentChunk.startTimeUs);
-      downstreamFormat = currentFormat;
     }
+    downstreamFormat = format;
 
     int result = sampleQueue.readData(formatHolder, buffer, loadingFinished, lastSeekPositionUs);
     if (result == FORMAT_READ) {

library/src/main/java/com/google/android/exoplayer/extractor/wav/WavHeaderReader.java

@@ -65,18 +65,14 @@ import java.io.IOException;
       return null;
     }
 
-    // If a bext chunk is present, skip it. Otherwise we expect a format chunk.
+    // Skip chunks until we find the format chunk.
     chunkHeader = ChunkHeader.peek(input, scratch);
-    if (chunkHeader.id == Util.getIntegerCodeForString("bext")) {
+    while (chunkHeader.id != Util.getIntegerCodeForString("fmt ")) {
       input.advancePeekPosition((int) chunkHeader.size);
       chunkHeader = ChunkHeader.peek(input, scratch);
     }
 
-    if (chunkHeader.id != Util.getIntegerCodeForString("fmt ")) {
-      throw new ParserException("Expected format chunk; found: " + chunkHeader.id);
-    }
     Assertions.checkState(chunkHeader.size >= 16);
-
     input.peekFully(scratch.data, 0, 16);
     scratch.setPosition(0);
     int type = scratch.readLittleEndianUnsignedShort();
@@ -88,11 +84,8 @@ import java.io.IOException;
 
     int expectedBlockAlignment = numChannels * bitsPerSample / 8;
     if (blockAlignment != expectedBlockAlignment) {
-      throw new ParserException(
-          "Expected WAV block alignment of: "
-              + expectedBlockAlignment
-              + "; got: "
-              + blockAlignment);
+      throw new ParserException("Expected block alignment: " + expectedBlockAlignment + "; got: "
+          + blockAlignment);
     }
     if (bitsPerSample != 16) {
       Log.e(TAG, "Only 16-bit WAVs are supported; got: " + bitsPerSample);

library/src/main/java/com/google/android/exoplayer/hls/HlsSampleSource.java

@@ -307,12 +307,12 @@ public final class HlsSampleSource implements SampleSource, Loader.Callback {
       mediaChunks.removeFirst();
     }
     HlsMediaChunk currentChunk = mediaChunks.getFirst();
-    Format currentFormat = currentChunk.format;
-    if (downstreamFormat == null || !downstreamFormat.equals(currentFormat)) {
-      eventDispatcher.downstreamFormatChanged(currentFormat, currentChunk.trigger,
+    Format format = currentChunk.format;
+    if (!format.equals(downstreamFormat)) {
+      eventDispatcher.downstreamFormatChanged(format, currentChunk.trigger,
           currentChunk.startTimeUs);
-      downstreamFormat = currentFormat;
     }
+    downstreamFormat = format;
 
     return sampleQueues[group].readData(formatHolder, buffer, loadingFinished, lastSeekPositionUs);
   }