The Chrome DevTools timeline gives a solid overview of the construction of each page. You can see the progression of grabbing network assets, Parsing HTML, Recalculating styles, Layout (aka reflow), Paint, Compositing

Here's a trace of this page, for example: http://paulirish.com/i/dd8f40.png

A far more low-level view is available in about:tracing - More on that here http://www.html5rocks.com/en/tutorials/games/abouttracing/