[vm, profiler] Remove race between sample processor and stub code initialization.

TEST=tsan
Bug: #54226
Change-Id: I54ce983acae28474c4a31200922b902dd19cf95d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/339643
Reviewed-by: Ben Konyi <[email protected]>
Commit-Queue: Ryan Macnak <[email protected]>

Author: rmacnak-google

runtime/vm/dart.cc

@@ -342,7 +342,6 @@ char* Dart::DartInit(const Dart_InitializeParams* params) {
   ForwardingCorpse::Init();
   Api::Init();
   NativeSymbolResolver::Init();
-  NOT_IN_PRODUCT(Profiler::Init());
   UnwindingRecordsPlatform::Init();
   Page::Init();
   StoreBuffer::Init();
@@ -486,6 +485,7 @@ char* Dart::DartInit(const Dart_InitializeParams* params) {
     vm_isolate_group()->heap()->Verify("Dart::DartInit", kRequireMarked);
 #endif
   }
+  NOT_IN_PRODUCT(Profiler::Init());
   // Allocate the "persistent" scoped handles for the predefined API
   // values (such as Dart_True, Dart_False and Dart_Null).
   Api::InitHandles();

runtime/vm/profiler.cc

@@ -1895,6 +1895,8 @@ void SampleBlockProcessor::ThreadMain(uword parameters) {
     }
 
     IsolateGroup::ForEach([&](IsolateGroup* group) {
+      if (group == Dart::vm_isolate_group()) return;
+
       const bool kBypassSafepoint = false;
       Thread::EnterIsolateGroupAsHelper(group, Thread::kSampleBlockTask,
                                         kBypassSafepoint);