Reland "[cpu-profiler] Fix a bug which caused a pure virtual function call"

This is a reland of c92a1dda

Original change's description:
> [cpu-profiler] Fix a bug which caused a pure virtual function call
>
> 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}

TBR=yangguo@chromium.org

Bug: v8:8346, v8:5193
Change-Id: I9878f65c868ff1aed6f3a587cba688c4241bad8c
Reviewed-on: https://chromium-review.googlesource.com/c/1298893Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56976}

src/libsampler/sampler.cc

@@ -615,13 +615,18 @@ Sampler::Sampler(Isolate* isolate)
   data_ = new PlatformData;
 }
 
-Sampler::~Sampler() {
-  DCHECK(!IsActive());
+void Sampler::UnregisterIfRegistered() {
 #if defined(USE_SIGNALS)
   if (IsRegistered()) {
     SamplerManager::instance()->RemoveSampler(this);
+    SetRegistered(false);
   }
 #endif
+}
+
+Sampler::~Sampler() {
+  DCHECK(!IsActive());
+  DCHECK(!IsRegistered());
   delete data_;
 }
 

src/libsampler/sampler.h

@@ -60,6 +60,12 @@ class Sampler {
   // with the CpuProfiler.
   bool IsRegistered() const { return base::Relaxed_Load(&registered_) != 0; }
 
+  // The sampler must be unregistered with the SamplerManager before ~Sampler()
+  // is called. If this doesn't happen, the signal handler might interrupt
+  // during the destructor and call DoSample(), which calls the pure virtual
+  // function Sampler::SampleStack(), causing a crash.
+  void UnregisterIfRegistered();
+
   void DoSample();
 
   void SetHasProcessingThread(bool value) {

src/profiler/cpu-profiler.cc

@@ -65,6 +65,7 @@ SamplingEventsProcessor::SamplingEventsProcessor(Isolate* isolate,
 
 SamplingEventsProcessor::~SamplingEventsProcessor() {
   sampler_->DecreaseProfilingDepth();
+  sampler_->UnregisterIfRegistered();
 }
 
 ProfilerEventsProcessor::~ProfilerEventsProcessor() = default;