static IntSet makeDomFrontSet(int szBlocks) {
    return szBlocks <= DOMFRONT_SET_THRESHOLD_SIZE ? new BitIntSet(szBlocks) : new ListIntSet();
  }
Make IntSet for the dominance-frontier sets.

@param szBlocks {@code >=0;} count of basic blocks in method
@return {@code non-null;} appropriate set
android/android_framework/dex-maker/src/main/java/com/android/dx/ssa/SetFactory.java