Fix handling of unresolved upper bounds in factory declarations (issue 721).

runtime/vm/parser.cc

Index: runtime/vm/parser.cc
===================================================================
--- runtime/vm/parser.cc	(revision 2197)
+++ runtime/vm/parser.cc	(working copy)
@@ -2346,8 +2346,9 @@
                                                        *(member.name)));
       const Class& signature_class = Class::Handle(
           Class::New(String::Handle(String::NewSymbol(":factory_signature")),
-                     Script::Handle()));
+                     script_));
       signature_class.set_is_finalized();
+      signature_class.set_library(library_);
       unresolved_factory_class.set_factory_signature_class(signature_class);
       // The type arguments of the result type are set during finalization.
       const TypeArguments& args = TypeArguments::Handle();
@@ -2762,7 +2763,8 @@
         UnresolvedClass::New(factory_pos, qualifier, *(factory_name.ident)));
     const Class& signature_class = Class::Handle(
         Class::New(String::Handle(String::NewSymbol(":factory_signature")),
-                   Script::Handle()));
+                   script_));
+    signature_class.set_library(library_);
     signature_class.set_is_finalized();
     ParseTypeParameters(signature_class);
     unresolved_factory_class.set_factory_signature_class(signature_class);