[Safari 10] Large heap memory

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First noticed in phetsims/plinko-probability#96, where you can find relevant details in the context of plinks-probability.

The Safari heap size is 2x-3x larger than Chrome. And it was determined that this is not sim-specific, it affects all sims.

Assigning to @ariel-phet to assign and prioritize. Since this affects all sims, and Safari 10 is relatively new, highly recommended to investigate soon.

[ariel-phet]

From the original issue:

It is a general problem with how Safari (old & new) is allocating the memory at sim start.

@jonathanolson please add clarifying/investigation comments/

Since this issue does not appear to be visibly affecting sim performance, marking medium priority, but would be good to understand more.