private void rebuildLabelToIndex() {
    int szItems = size();

    for (int i = 0; i < szItems; i++) {
      LabeledItem li = (LabeledItem) get0(i);

      if (li != null) {
        labelToIndex.set(li.getLabel(), i);
      }
    }
  }
Rebuilds the label-to-index mapping after a {@code shrinkToFit()}. Note: This assumes that the
labels that are in the list are the same, although the indicies may have changed.
android/android_framework/dex-maker/src/main/java/com/android/dx/util/LabeledList.java