For HLS segment sniffing, fall back on extractor creation by file extension

This reduces the possiblity of regressions.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=213436912

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/DefaultHlsExtractorFactory.java

@@ -28,7 +28,6 @@ import com.google.android.exoplayer2.extractor.ts.Ac3Extractor;
 import com.google.android.exoplayer2.extractor.ts.AdtsExtractor;
 import com.google.android.exoplayer2.extractor.ts.AdtsExtractor;
 import com.google.android.exoplayer2.extractor.ts.DefaultTsPayloadReaderFactory;
 import com.google.android.exoplayer2.extractor.ts.DefaultTsPayloadReaderFactory;
 import com.google.android.exoplayer2.extractor.ts.TsExtractor;
 import com.google.android.exoplayer2.extractor.ts.TsExtractor;
-import com.google.android.exoplayer2.source.UnrecognizedInputFormatException;
 import com.google.android.exoplayer2.util.MimeTypes;
 import com.google.android.exoplayer2.util.MimeTypes;
 import com.google.android.exoplayer2.util.TimestampAdjuster;
 import com.google.android.exoplayer2.util.TimestampAdjuster;
 import java.io.EOFException;
 import java.io.EOFException;
@@ -145,8 +144,8 @@ public final class DefaultHlsExtractorFactory implements HlsExtractorFactory {
       }
       }
     }
     }
 
 
-    throw new UnrecognizedInputFormatException(
-        "The segment does not seem to conform to any of the known HLS segment formats", uri);
+    // Fall back on the extractor created by file extension.
+    return buildResult(extractorByFileExtension);
   }
   }
 
 
   private Extractor createExtractorByFileExtension(
   private Extractor createExtractorByFileExtension(