Tests that debugger StepInto will stop inside next timeout handler.

Set timer for test function.
Call stack:
    0) callback1 (debugger-step-into-across-timeouts.js:21)
    [setTimeout]
    0) testFunction (debugger-step-into-across-timeouts.js:15)
    [setTimeout]
    0) scheduleTestFunction <omitted>
    <... skipped remaining frames ...>

Executing StepInto...
Executing StepInto...
Call stack:
    0) callback2 (debugger-step-into-across-timeouts.js:26)
    [setTimeout]
    0) callback1 (debugger-step-into-across-timeouts.js:20)
    [setTimeout]
    0) testFunction (debugger-step-into-across-timeouts.js:15)
    [setTimeout]
    0) scheduleTestFunction <omitted>
    <... skipped remaining frames ...>