Do not record CPU profile samples when stack collection is failed.

src/profiler/sampler.cc

Index: src/profiler/sampler.cc
diff --git a/src/profiler/sampler.cc b/src/profiler/sampler.cc
index 45f1d4d3efcfd726409b16ec2aa80f0b673b0d92..60397b6fc1c12b281a7604174ce04effe4b4b578 100644
--- a/src/profiler/sampler.cc
+++ b/src/profiler/sampler.cc
@@ -701,6 +701,11 @@ DISABLE_ASAN void TickSample::Init(Isolate* isolate,
   GetStackSample(isolate, regs, record_c_entry_frame,
                  reinterpret_cast<void**>(&stack[0]), kMaxFramesCount, &info);
   frames_count = static_cast<unsigned>(info.frames_count);
+  if (!frames_count) {
+    // It is executing JS but failed to collect a stack trace.
+    // Mark the sample as spoiled.
+    pc = 0;
+  }
 }
 
 
@@ -797,7 +802,7 @@ void Sampler::SampleStack(const v8::RegisterState& state) {
   TickSample sample_obj;
   if (sample == NULL) sample = &sample_obj;
   sample->Init(isolate_, state, TickSample::kIncludeCEntryFrame, true);
-  if (is_counting_samples_) {
+  if (is_counting_samples_ && sample->pc) {
     if (sample->state == JS) ++js_sample_count_;
     if (sample->state == EXTERNAL) ++external_sample_count_;
   }