I started such a project a while ago, I am extremely busy at the moment, but as things calm down in the real world I'll have more time to get it to a releasable state.
Without giving away too much information (I don't wanna promise things I can't deliver)... It renders parts at the moment. I still need to work on adding directional lighting for the shading to look like it's from this decade, but it works.
I'm writing almost the entire thing from scratch, not relying on any existing (generic) WebGL libraries. I've written the shaders from scratch to be as optimized as possible for use specific to LDraw. The only external library I used was glMatrix. We don't have fancy textures or anything, but we have TONS of polygons, for example a simple 4x2 brick has 472 lines and 700 triangles. To completely render a frame in the canvas from start to finish (with only a 2x4 brick) takes about 6ms in chrome, and 22ms in firefox.