Bug 207297

Basic repro: ``` let count1 = 0; let key1 = { toString() { count1++; return 'foo'; } }; ({ [key1]: 'bar' }); let count2 = 0; let key2 = { toString() { count2++; return 'foo'; } }; ({ [key2]() { return 'bar'; } }); print(count1, count2); ``` λ eshost -s test.js #### ch, sm, v8, xs 1 1 #### jsc 1 2 Notes: - This also reproes if: - we write the function property as `[key]: function () { return 'bar'; }` or `[key]: () => 'bar'` instead - we set toString to null and use valueOf instead - Relevant test262 failures: https://github.com/tc39/test262/blob/master/test/language/computed-property-names/to-name-side-effects/class.js https://github.com/tc39/test262/blob/master/test/language/computed-property-names/to-name-side-effects/numbers-class.js https://github.com/tc39/test262/blob/master/test/language/computed-property-names/to-name-side-effects/object.js - Bug 170934 seems related but separate.