I also suggest zooming into those graphs to see which changes lead to drops (at least those that are currently visible). Then you could try to explain people what asm.js specific is in changes like:
[hint: nothing, they have more to do with how Emscripten has a tendency to produce extremely big functions which no human would write, and JIT has to accomodate for that to hit them in correct moment and not give up on them. Once it hits them however the optimizations that were there for ages, optimizations purely based on JavaScript semantics, start doing what they are intended to do --- make JavaScript run fast]
https://code.google.com/p/v8/source/detail?r=14658 and https://code.google.com/p/v8/source/detail?r=15147
[hint: nothing, they have more to do with how Emscripten has a tendency to produce extremely big functions which no human would write, and JIT has to accomodate for that to hit them in correct moment and not give up on them. Once it hits them however the optimizations that were there for ages, optimizations purely based on JavaScript semantics, start doing what they are intended to do --- make JavaScript run fast]