1-2% on a large scale is pretty significant. If each request on average takes, say, a second, and is then reduced by 1-2%, that'd be 990ms. 10ms saved per request.
Let's say that on average, 5 uncached pages are opened per day per chrome-mobile user. I don't feel like looking up the total amount of Chrome-mobile users, let's estimate that at 500 million.
5 page loads * 500,000,000 users * 10 ms = 25000000000ms per day saved, that's 289 days of page loading saved on a global scale per day.
I don't personally think measuring the improvement in terms of time is very interesting, it's very hard to interpret, but each ms of loading takes up a certain percentage of your battery, the amount of electricity saved daily on a global scale because of an improvement of 1-2% is fairly significant.
Only if your phone is spending all its time parsing javascript, and maybe 1% (being generous) of its CPU time is spent doing that for a JS heavy page. So 1% of 1%. Really not much at all.
