Track async causal stack traces

runtime/vm/intrinsifier_ia32.cc

Index: runtime/vm/intrinsifier_ia32.cc
diff --git a/runtime/vm/intrinsifier_ia32.cc b/runtime/vm/intrinsifier_ia32.cc
index 6c0f6a11fcb2a8a2be2b8d933a9dbae5d45d88b5..13e47bdd0c2d142aa4b15efadf197c4f961ea8c7 100644
--- a/runtime/vm/intrinsifier_ia32.cc
+++ b/runtime/vm/intrinsifier_ia32.cc
@@ -2316,6 +2316,20 @@ void Intrinsifier::Timeline_isDartStreamEnabled(Assembler* assembler) {
   __ ret();
 }
 
+
+void Intrinsifier::ClearAsyncThreadStackTrace(Assembler* assembler) {
+  __ LoadObject(EAX, Object::null_object());
+  __ movl(Address(THR, Thread::async_stack_trace_offset()), EAX);
+  __ ret();
+}
+
+
+void Intrinsifier::SetAsyncThreadStackTrace(Assembler* assembler) {
+  __ movl(Address(THR, Thread::async_stack_trace_offset()), EAX);
+  __ LoadObject(EAX, Object::null_object());
+  __ ret();
+}
+
 #undef __
 
 }  // namespace dart