Rework standalone to use a synchronous loader that does not invoke Dart code

runtime/bin/builtin_common.cc

Index: runtime/bin/builtin_common.cc
diff --git a/runtime/bin/builtin_common.cc b/runtime/bin/builtin_common.cc
index 678e48b7163fac199fded9d936144649417ac2a6..bbf9788506ae6bdd5c6ae201ac1c891f576f9faf 100644
--- a/runtime/bin/builtin_common.cc
+++ b/runtime/bin/builtin_common.cc
@@ -40,6 +40,11 @@ Dart_Handle Builtin::SetLoadPort(Dart_Port port) {
   RETURN_IF_ERROR(send_port);
   Dart_Handle result = Dart_SetField(builtin_lib, field_name, send_port);
   RETURN_IF_ERROR(result);
+  // Also set the _isolateId field.
+  result = Dart_SetField(builtin_lib,
+                         DartUtils::NewString("_isolateId"),
+                         Dart_NewInteger(Dart_GetMainPortId()));
+  RETURN_IF_ERROR(result);

[turnidge, 2016/06/03 17:50:24]

Would be nice if the function failed on a second call when this field fails to
set.  Maybe move this to the top of the function.

[Cutch, 2016/06/03 22:07:32]

Done.

   return Dart_True();
 }