Clean up more flags using flag list.

runtime/vm/ast.cc

Index: runtime/vm/ast.cc
diff --git a/runtime/vm/ast.cc b/runtime/vm/ast.cc
index bb1b624a6c3fe12d7872b824b3bbc001b343eeb7..7d7f3f4a145473e42ec56cf42c70a5ef25429400 100644
--- a/runtime/vm/ast.cc
+++ b/runtime/vm/ast.cc
@@ -13,14 +13,8 @@
 
 namespace dart {
 
-DEFINE_FLAG(bool, trace_ast_visitor, false,
-            "Trace AstVisitor.");
-
 #define DEFINE_VISIT_FUNCTION(BaseName)                                        \
 void BaseName##Node::Visit(AstNodeVisitor* visitor) {                          \
-  if (FLAG_trace_ast_visitor) {                                                \
-    THR_Print("Visiting %s\n", Name());                                        \
-  }                                                                            \
   visitor->Visit##BaseName##Node(this);                                        \
 }