Introduce is_debuggable state bit on function objects

runtime/vm/class_finalizer.cc

Index: runtime/vm/class_finalizer.cc
===================================================================
--- runtime/vm/class_finalizer.cc	(revision 42569)
+++ runtime/vm/class_finalizer.cc	(working copy)
@@ -1388,6 +1388,7 @@
                             cls,
                             field.token_pos()));
           getter.set_result_type(type);
+          getter.set_is_debuggable(false);
           cls.AddFunction(getter);
           field.set_value(Instance::Handle(I, Object::sentinel().raw()));
         }
@@ -2070,6 +2071,7 @@
       clone.SetNumOptionalParameters(func.NumOptionalParameters(),
                                      func.HasOptionalPositionalParameters());
       clone.set_result_type(dynamic_type);
+      clone.set_is_debuggable(false);
 
       const intptr_t num_parameters = func.NumParameters();
       // The cloned ctor shares the parameter names array with the