code: public void setIndexBuffer(GVRIndexBuffer ibuf)
      {
          mIndices = ibuf;
          NativeMesh.setIndexBuffer(getNative(), (ibuf != null) ? ibuf.getNative() : 0L);
      }
docs: Changes the index buffer associated with this mesh.
  @param ibuf new index buffer to use
  @see #setIndices(int[])
  @see #getIndexBuffer()
  @see #getIntIndices()