Combine a bunch of var statements into one inside Tree.prototype.Build; kill the TODO comment
Add vines -- to all trees, because has_vines_ is going to be hard to figure out since there's no world climate code yet.  Leave the early exit commented out.
Change the API between the vertices list and the buffer-building code, making each item in the list an object instead of an array: name the vertex, normal, uv, and model items (adding the last).  Don't set any model matrices in the .push() calls, but add a model matrix at the end of Build (which is a hack, but oh well).  Delete the TODO.