[vm] Do not interrupt mutator when SampleBlock is complete

This code was added when samples streaming was implemented and should
not be necessary. Let background thread drain samples instead.

This significantly reduces the overhead of activating profiler when
using NativeRuntime.streamTimelineTo from 2-3x to ~10% in AOT mode
and around ~20-25% in JIT.

TEST=ci

Change-Id: I4c6026f832d6a952b24323632b4126df6a6a6964
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/464183
Reviewed-by: Ryan Macnak <rmacnak@google.com>
Commit-Queue: Slava Egorov <vegorov@google.com>

runtime/vm/profiler.cc

@@ -909,12 +909,7 @@ Sample* SampleBlockBuffer::ReserveSampleImpl(Isolate* isolate,
   if (block != nullptr) {
     block->MarkCompleted();
     if (!Isolate::IsSystemIsolate(isolate)) {
-      Thread* mutator = isolate->IGNORE_RACE(mutator_thread)();
-      // The mutator thread might be NULL if we sample in the middle of
-      // Thread::Enter/ExitIsolate.
-      if ((mutator != nullptr) && isolate->TrySetHasCompletedBlocks()) {
-        mutator->ScheduleInterrupts(Thread::kVMInterrupt);
-      }
+      isolate->TrySetHasCompletedBlocks();
     }
   }
   return next->ReserveSample();

runtime/vm/thread.cc

@@ -857,13 +857,6 @@ ErrorPtr Thread::HandleInterrupts(uword interrupt_bits) {
     }
     heap()->CheckFinalizeMarking(this);
 
-#if !defined(PRODUCT)
-    // TODO(dartbug.com/60508): Allow profiling of isolate-group-shared code.
-    if (isolate() != nullptr && isolate()->TakeHasCompletedBlocks()) {
-      Profiler::ProcessCompletedBlocks(isolate());
-    }
-#endif  // !defined(PRODUCT)
-
 #if !defined(PRODUCT) || defined(FORCE_INCLUDE_SAMPLING_HEAP_PROFILER)
     HeapProfileSampler& sampler = heap_sampler();
     if (sampler.ShouldSetThreadSamplingInterval()) {