Do not mix up callstacks in pprof output.
Do not mix up callstacks in pprof output.

For dump_at_max, we would filter out all rows for some callstacks, so we
would use whatever row came after that.

We had an assertion that was supposed to protect against this, which
sadly was a tautology instead.

Bug: 164995430
Change-Id: I834cbeac4ec176b8ccad88619a793b882f533b03
google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto