private String prefixTag(String tag) {
    if (mApplicationTag != null) {
      return mApplicationTag + ":" + tag;
    } else {
      return tag;
    }
  }
Note: this gets forwarded to {@code android.util.Log.e} as {@code android.util.Log.wtf} might
crash the app.
fbcore/src/main/java/com/facebook/common/logging/FLogDefaultLoggingDelegate.java