Why is it so hard to find? Just search the Rotor source for "WriteBarrier". The JIT inserts calls to some helper functions named something like JIT_WriteBarrier. These functions can be found in a file named jithelp.asm.
And for the record: .NET does the same thing. You can see those helper calls with a native debugger.
Are you sure it's about layout and not rendering? It looks to me (yes, I ran into the same issue) that's the same bug from the beta versions where parts of the page were not rendered until you clicked them. Kind of scary for this to happen in a "release
Care to show me a browser that doesn't use 50 megabytes for a page (tab)? . It's funny because I keep seeing browser users complaining about their browser (IE, Firefox etc.) consuming a lot of memory but if you open the same web page in all of them and
then take a closer look at various memory numbers you see that at the end of the day they all use tens of megabytes of memory. For example
http://channel9.msdn.com (private bytes usage as reported by ProcessExplorer running on Vista):