Tests asynchronous call stacks for MutationObserver.

Set timer for test function.
Captured call stacks in no particular order:
Call stack:
    0) mutationCallback (async-callstack-mutation-observer.js:26)
    [attributes]
    0) doMutations1 (async-callstack-mutation-observer.js:55)
    1) timeout1 (async-callstack-mutation-observer.js:49)
    [setTimeout]
    0) testFunction (async-callstack-mutation-observer.js:40)
    [setTimeout]
    0) scheduleTestFunction <omitted>
    <... skipped remaining frames ...>

Call stack:
    0) mutationCallback (async-callstack-mutation-observer.js:26)
    [childList]
    0) doMutations2 (async-callstack-mutation-observer.js:69)
    1) timeout2 (async-callstack-mutation-observer.js:62)
    [setTimeout]
    0) timeout1 (async-callstack-mutation-observer.js:48)
    [setTimeout]
    0) testFunction (async-callstack-mutation-observer.js:40)
    [setTimeout]
    0) scheduleTestFunction <omitted>
    <... skipped remaining frames ...>

Call stack:
    0) nestedMutationCallback (async-callstack-mutation-observer.js:33)
    [attributes]
    0) doMutations1 (async-callstack-mutation-observer.js:55)
    1) mutationCallback (async-callstack-mutation-observer.js:25)
    [attributes]
    0) doMutations1 (async-callstack-mutation-observer.js:55)
    1) timeout1 (async-callstack-mutation-observer.js:49)
    [setTimeout]
    0) testFunction (async-callstack-mutation-observer.js:40)
    [setTimeout]
    0) scheduleTestFunction <omitted>
    <... skipped remaining frames ...>

Call stack:
    0) nestedMutationCallback (async-callstack-mutation-observer.js:33)
    [childList]
    0) doMutations2 (async-callstack-mutation-observer.js:69)
    1) timeoutFromNestedMutation (async-callstack-mutation-observer.js:81)
    [setTimeout]
    0) nestedMutationCallback (async-callstack-mutation-observer.js:35)
    [attributes]
    0) doMutations1 (async-callstack-mutation-observer.js:55)
    1) mutationCallback (async-callstack-mutation-observer.js:25)
    [attributes]
    0) doMutations1 (async-callstack-mutation-observer.js:55)
    1) timeout1 (async-callstack-mutation-observer.js:49)
    [setTimeout]
    0) testFunction (async-callstack-mutation-observer.js:40)
    [setTimeout]
    0) scheduleTestFunction <omitted>
    <... skipped remaining frames ...>

Call stack:
    0) timeoutFromMutation (async-callstack-mutation-observer.js:75)
    [setTimeout]
    0) mutationCallback (async-callstack-mutation-observer.js:28)
    [attributes]
    0) doMutations1 (async-callstack-mutation-observer.js:55)
    1) timeout1 (async-callstack-mutation-observer.js:49)
    [setTimeout]
    0) testFunction (async-callstack-mutation-observer.js:40)
    [setTimeout]
    0) scheduleTestFunction <omitted>
    <... skipped remaining frames ...>

Call stack:
    0) timeoutFromNestedMutation (async-callstack-mutation-observer.js:80)
    [setTimeout]
    0) nestedMutationCallback (async-callstack-mutation-observer.js:35)
    [attributes]
    0) doMutations1 (async-callstack-mutation-observer.js:55)
    1) mutationCallback (async-callstack-mutation-observer.js:25)
    [attributes]
    0) doMutations1 (async-callstack-mutation-observer.js:55)
    1) timeout1 (async-callstack-mutation-observer.js:49)
    [setTimeout]
    0) testFunction (async-callstack-mutation-observer.js:40)
    [setTimeout]
    0) scheduleTestFunction <omitted>
    <... skipped remaining frames ...>