private static String getStackTraceString(@Nullable Throwable tr) {
    if (tr == null) {
      return "";
    }

    final String stackTrace = Log.getStackTraceString(tr);
    return stackTrace;
  }
Get a loggable stack trace from a Throwable

@param tr An exception to log
imagepipeline/src/main/java/com/facebook/imagepipeline/core/CloseableReferenceFactory.java