1. Dynamic compute the main closure that needs to be run by the main isolate

runtime/vm/object.cc

Index: runtime/vm/object.cc
diff --git a/runtime/vm/object.cc b/runtime/vm/object.cc
index db19ab39c99ae3623a34b8d0ea12fb4bc7aa0b99..728e2ffe6446a8833d056194b9aef8d727408440 100644
--- a/runtime/vm/object.cc
+++ b/runtime/vm/object.cc
@@ -12063,6 +12063,32 @@ RawFunction* Library::GetFunction(const GrowableArray<Library*>& libs,
 }
 
 
+RawObject* Library::GetFunctionClosure(const String& name) const {
+  Thread* thread = Thread::Current();
+  Zone* zone = thread->zone();
+  Function& func = Function::Handle(zone, LookupFunctionAllowPrivate(name));
+  if (func.IsNull()) {
+    // Check whether the function is reexported into the library.
+    const Object& obj = Object::Handle(zone, LookupReExport(name));
+    if (obj.IsFunction()) {
+      func ^= obj.raw();
+    } else {
+      // Check if there is a getter of 'name', in which case invoke it
+      // and return the result.
+      const String& getter_name = String::Handle(zone, Field::GetterName(name));
+      func = LookupFunctionAllowPrivate(getter_name);
+      if (func.IsNull()) {
+        return Closure::null();
+      }
+      // Invoke the getter and return the result.
+      return DartEntry::InvokeFunction(func, Object::empty_array());
+    }
+  }
+  func = func.ImplicitClosureFunction();
+  return func.ImplicitStaticClosure();
+}
+
+
 #if defined(DART_NO_SNAPSHOT) && !defined(PRODUCT)
 void Library::CheckFunctionFingerprints() {
   GrowableArray<Library*> all_libs;