Add token index position to classes and types for more accurate error reporting.

runtime/vm/unit_test.cc

Index: runtime/vm/unit_test.cc
===================================================================
--- runtime/vm/unit_test.cc	(revision 3925)
+++ runtime/vm/unit_test.cc	(working copy)
@@ -136,7 +136,8 @@
   // frame walking can be used.
   Class& cls = Class::ZoneHandle();
   const Script& script = Script::Handle();
-  cls = Class::New(function_name, script);
+  const intptr_t kPos = 1;  // Dummy token index in non-existing source.
+  cls = Class::New(function_name, script, kPos);
   const Array& functions = Array::Handle(Array::New(1));
   functions.SetAt(0, function_);
   cls.SetFunctions(functions);