message: demo: Reduce the resize() cost in simplify/simplifySloppy
  We can resize the target array to a size that's guaranteed to be
  sufficient - which is the minimum of original vertex count and resulting
  index count. For simplifications with a small ratio this basically
  eliminates the cost of compacting the buffer.
diff: @@ -369,7 +369,7 @@ void simplify(const Mesh& mesh, float threshold = 0.2f)
  lod.indices.resize(mesh.indices.size()); // note: simplify needs space for index_count elements in the destination array, not target_index_count
  lod.indices.resize(meshopt_simplify(&lod.indices[0], &mesh.indices[0], mesh.indices.size(), &mesh.vertices[0].px, mesh.vertices.size(), sizeof(Vertex), target_index_count, target_error));
  - lod.vertices.resize(mesh.vertices.size());
  + lod.vertices.resize(lod.indices.size() < mesh.vertices.size() ? lod.indices.size() : mesh.vertices.size()); // note: this is just to reduce the cost of resize()
  lod.vertices.resize(meshopt_optimizeVertexFetch(&lod.vertices[0], &lod.indices[0], lod.indices.size(), &mesh.vertices[0], mesh.vertices.size(), sizeof(Vertex)));
  double end = timestamp();
  @@ -387,10 +387,10 @@ void simplifySloppy(const Mesh& mesh, float threshold = 0.2f)
  size_t target_index_count = size_t(mesh.indices.size() * threshold);
  - lod.indices.resize(target_index_count);
  + lod.indices.resize(target_index_count); // note: simplifySloppy, unlike simplify, is guaranteed to output results that don't exceed the requested target_index_count
  lod.indices.resize(meshopt_simplifySloppy(&lod.indices[0], &mesh.indices[0], mesh.indices.size(), &mesh.vertices[0].px, mesh.vertices.size(), sizeof(Vertex), target_index_count));
  - lod.vertices.resize(mesh.vertices.size());
  + lod.vertices.resize(lod.indices.size() < mesh.vertices.size() ? lod.indices.size() : mesh.vertices.size()); // note: this is just to reduce the cost of resize()
  lod.vertices.resize(meshopt_optimizeVertexFetch(&lod.vertices[0], &lod.indices[0], lod.indices.size(), &mesh.vertices[0], mesh.vertices.size(), sizeof(Vertex)));
  double end = timestamp();
  