Javadoc for FakeExtractorOutput.WRITE_DUMP.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=128045581

testutils/src/main/java/com/google/android/exoplayer2/testutil/FakeExtractorOutput.java

@@ -32,6 +32,11 @@ import java.io.PrintWriter;
  */
 public final class FakeExtractorOutput implements ExtractorOutput, Dumper.Dumpable {
 
+  /**
+   * If true, makes {@link #assertOutput(Instrumentation, String)} method write dump result to 
+   * {@code /sdcard/Android/data/apk_package/ + dumpfile} file instead of comparing it with an 
+   * existing file.
+   */
   private static final boolean WRITE_DUMP = false;
 
   private final boolean allowDuplicateTrackIds;