Pass isolate to AST ID functions.

src/scopes.h

Index: src/scopes.h
diff --git a/src/scopes.h b/src/scopes.h
index 031ea3d16b66067f32ad0d65be0fe77906901892..e76fb50598c3a6267576a30a8970a626938e970c 100644
--- a/src/scopes.h
+++ b/src/scopes.h
@@ -425,6 +425,10 @@ class Scope: public ZoneObject {
   // Construct a catch scope with a binding for the name.
   Scope(Scope* inner_scope, Handle<String> catch_variable_name);
 
+  inline Slot* NewSlot(Variable* var, Slot::Type type, int index) {
+    return new(isolate_->zone()) Slot(isolate_, var, type, index);
+  }
+
   void AddInnerScope(Scope* inner_scope) {
     if (inner_scope != NULL) {
       inner_scopes_.Add(inner_scope);