Chrome has a staggering amount of C++ code. It's not all heavily hand-optimized. Probably very little of it is optimized at all, or needs to be. They're relyin

Chrome has a staggering amount of C++ code. It's not all heavily hand-optimized. Probably very little of it is optimized at all, or needs to be. They're relying on the compiler working its magic to make non-hand-optimized code run pretty fast. That's fine, but it requires you to expose a lot of stuff in headers and that slows down compilation. I'm fairly sure, like other commenters, that they could speed up compilation a lot and impact performance very little by carefully modularizing their header files. But that's a really big job.