In current implementation we don't support nested scheduled break at all. If one break was scheduled inside another and second one doesn't produce actual break (execution was in blackboxed code or no JavaScript was executed) then second one will clear first scheduled break even if any not blackboxed JavaScript will be executed later.
Ambiguous break reason is added for the case when we have more then one scheduled reason. "auxData" in this case contains object with array of { reason: reason, auxData: auxData } objects for each reason in 'reasons' property.
BUG=chromium:632405
Review-Url: https://codereview.chromium.org/2678313002
Cr-Commit-Position: refs/heads/master@{#43021}
