We need to remove each Sampler from the SamplerManager before we call
the Sampler destructor. This is because the signal handler can interrupt
the destructor, and call DoSampler(), which calls sampler->SampleStack()
on the sampler being destructed, causing general unhappiness and
"Pure virtual function called!" crashes.

Bug: v8:8346, v8:5193
Change-Id: Iaa595a196eab33fb1af31584e9a68fd1ce0a18f6
Reviewed-on: https://chromium-review.googlesource.com/c/1293949
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Reviewed-by: Alexei Filippov <alph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56882}