(or, we need to build the Minix to WebKit's Linux, and here's why)
TL;DR: Webkit is insanely complicated. We need an educational system like Minix for the browser so we can teach, learn and build a faster and better web.
961,221 lines of code.
Look at the difference between the Linux and Minix kernels. Linux is 14,000,000 lines of code and growing, while Minix ostensibly accomplishes the same goals in about 3800 lines of code. This suggests that the essential complexity of a kernel might be two orders of magnitude less than the complexity of Linux.
By analogy, it seems as though WebCore's rendering engine might have a much smaller Kolmogorov complexity than its 75,000 lines of code would imply. Another example, a programmer's editor: Vim vs Vi. Vim is a million lines of code, while BSD ex-vi is about 18,000, and most people still don't even maximize the efficiency of vi.
In the past few months I've been fascinated by the complexity of the systems I use every day and I'm trying to get an intuitive sense of their "essential complexity" compared to their complexity as implemented.
There are minimal "hackable" versions of terminals, kernels, and text editors, but we don't have a browser built with simplicity or teachability in mind. Minix helped Linus learn how kernels work, and we got Linux out of it. What could a smart student do given a browser designed with the same goals?
Because the web is so important to us, I think it's becoming extremely important for us to understand its core technologies at a deeper level. One of the best ways we could move forward in pursuit of that goal would be building a browser that aims to be the Minix to WebKit's Linux.
With a system like this, we'd make it possible for users to pop the hood and tinker for learning or leisure.
We'd lower one of the biggest barriers that keep people from being able to contribute to the improvement of their computers.
We'd facilitate faster prototyping and a quicker response cycle for the W3C, the web standards body, making the standards process better for all involved.
We could permanently move the needle on the rate at which we improve the web.
(Edit: after reading some of the comments, I realize that I sacrificed too much of my argument in the pursuit of conciseness. Hopefully, this fills in some of the gaps.)
What I actually think the community would be capable of building in a reasonable amount of time is a rendering and layout engine for HTML5/CSS3, not a full-out reimplementation of WebKit in two orders of magnitude less code.
As a student reading the source code, I want to know how we do this. What heuristics do we use that are most effective? In what places could they be made better? What portions of them are still implemented for legacy reasons?
The only thing I know how to relate this to is perhaps the bin-packing problem, which is known to be NP-hard.
Minix3 is two orders of magnitude smaller than Linux because it tightly controls the scope of the problem (memory management, device management, and system calls) in the interest of teachability and security.
In the same way, I think we can build a teachable, well-engineered rendering/layout engine in < 20,000 lines of code. By comparison, the rendering engine in NetSurf (an open-source browser designed for RISC OS) is about 5400 lines of code.
If you're interested and want to discuss this further, I'm @_bolted on Twitter. Let's talk.
(I'm currently working on checkit.co, a service that automates scheduling Google Calendar events.)