Implement safepointing of threads

runtime/vm/dart_api_impl.h

Index: runtime/vm/dart_api_impl.h
diff --git a/runtime/vm/dart_api_impl.h b/runtime/vm/dart_api_impl.h
index 6172e1a9433fbc74a0133ff214db0698fdcf2fdc..ee36410d6512685881ef23da9a470753b8d1cdac 100644
--- a/runtime/vm/dart_api_impl.h
+++ b/runtime/vm/dart_api_impl.h
@@ -8,6 +8,7 @@
 #include "vm/allocation.h"
 #include "vm/native_arguments.h"
 #include "vm/object.h"
+#include "vm/safepoint.h"
 
 namespace dart {
 
@@ -51,11 +52,12 @@ const char* CanonicalFunction(const char* func);
       FATAL1("%s expects to find a current scope. Did you forget to call "     \
            "Dart_EnterScope?", CURRENT_FUNC);                                  \
     }                                                                          \
-  } while (0)
+  } while (0);                                                                 \
 
 #define DARTSCOPE(thread)                                                      \
   Thread* T = (thread);                                                        \
   CHECK_API_SCOPE(T);                                                          \
+  TransitionNativeToVM trainsition(T);                                         \
   HANDLESCOPE(T);