(#3040) - tweaks to perf tests

Justification for these changes:

* 10 iterations is way too many for `temp-views`; it doesn't even finish in Travis for Firefox, and that's because it's already really slow even with just one iteration. My perf report showed numbers for 1 iteration, and you can see they still take ~10x longer than the other tests..
* For Safari you need to request a huge size up-front so that the popup doesn't appear during the test and throw off your numbers.