Clean up DefaultAudioSink

This is a first step towards factoring out position tracking functionality.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=189027731

library/core/src/main/java/com/google/android/exoplayer2/util/Util.java

@@ -942,6 +942,20 @@ public final class Util {
   }
 
   /**
+   * Returns whether {@code encoding} is one of the PCM encodings.
+   *
+   * @param encoding The encoding of the audio data.
+   * @return Whether the encoding is one of the PCM encodings.
+   */
+  public static boolean isEncodingPcm(@C.Encoding int encoding) {
+    return encoding == C.ENCODING_PCM_8BIT
+        || encoding == C.ENCODING_PCM_16BIT
+        || encoding == C.ENCODING_PCM_24BIT
+        || encoding == C.ENCODING_PCM_32BIT
+        || encoding == C.ENCODING_PCM_FLOAT;
+  }
+
+  /**
    * Returns whether {@code encoding} is high resolution (> 16-bit) integer PCM.
    *
    * @param encoding The encoding of the audio data.