Move _fatal to dart:async

runtime/lib/object.cc

Index: runtime/lib/object.cc
diff --git a/runtime/lib/object.cc b/runtime/lib/object.cc
index 9c20eebdab0c2e4febc27a6f9d4907a57448c147..e5cb7e1c6a07686d4ff8097bcc8111d8a6e33f79 100644
--- a/runtime/lib/object.cc
+++ b/runtime/lib/object.cc
@@ -20,11 +20,11 @@ DECLARE_FLAG(bool, trace_type_checks);
 // Helper function in stacktrace.cc.
 void _printCurrentStackTrace();
 
-DEFINE_NATIVE_ENTRY(DartInternal_fatal, 1) {
-  // The SDK library code entered an unrecoverable state.
+DEFINE_NATIVE_ENTRY(DartAsync_fatal, 1) {
+  // The dart:async library code entered an unrecoverable state.
   const Instance& instance = Instance::CheckedHandle(arguments->NativeArgAt(0));
   const char* msg = instance.ToCString();
-  OS::PrintErr("Fatal error in the SDK libraries\n");
+  OS::PrintErr("Fatal error in dart:async: %s\n", msg);
   _printCurrentStackTrace();
   FATAL(msg);
   return Object::null();