It's more than just architecting the drawing commands and resource management. That's just the renderer.
The term "rendering engine" is misleading; in the context of browsers the rendering engine does basically all the core browser tasks. Basically, all the stuff needed to make a web page _work_ is part of the rendering engine. Stuff like history, bookmarks, URL bar, is part of the rest of the browser. See https://news.ycombinator.com/item?id=13331505
Servo's usage of Rust is all for the rest of the stuff. We do have a component, http://github.com/servo/webrender/, which handles rendering in particular. That indeed does the architecting of the draw commands and resource management on the CPU, and has a bunch of shaders handling everything else.
The term "rendering engine" is misleading; in the context of browsers the rendering engine does basically all the core browser tasks. Basically, all the stuff needed to make a web page _work_ is part of the rendering engine. Stuff like history, bookmarks, URL bar, is part of the rest of the browser. See https://news.ycombinator.com/item?id=13331505
Servo's usage of Rust is all for the rest of the stuff. We do have a component, http://github.com/servo/webrender/, which handles rendering in particular. That indeed does the architecting of the draw commands and resource management on the CPU, and has a bunch of shaders handling everything else.