Hi Smith,
Here are a lot of good reading materials for learning how Chromium works:
They are roughly ordered so the first 10 or so are really useful for understanding the different parts of the codebase.
Much of the browser (gui and multi-process) code is contained in the chrome/ directory.
WebKit (the html rendering engine) is in third_party/WebKit
There is a lot of utility code in base/ and net/.
-Patrick