Take ast node id counting away from Isolate.

src/parser.h

Index: src/parser.h
diff --git a/src/parser.h b/src/parser.h
index 4aa6f719f3b9361d7cf6a1622f4cc7cc8dd0f908..b23a74ee11fdda900247dfd174269681a87bd82c 100644
--- a/src/parser.h
+++ b/src/parser.h
@@ -378,17 +378,17 @@ class ParserTraits {
   explicit ParserTraits(Parser* parser) : parser_(parser) {}
 
   // Custom operations executed when FunctionStates are created and destructed.
-  template<typename FunctionState>
-  static void SetUpFunctionState(FunctionState* function_state, Zone* zone) {
-    Isolate* isolate = zone->isolate();
-    function_state->saved_ast_node_id_ = isolate->ast_node_id();
-    isolate->set_ast_node_id(BailoutId::FirstUsable().ToInt());
+  template <typename FunctionState>
+  static void SetUpFunctionState(FunctionState* function_state) {
+    function_state->saved_ast_node_id_ = function_state->ast_node_id_gen_->id();
+    function_state->ast_node_id_gen_->set_id(BailoutId::FirstUsable().ToInt());
   }
 
-  template<typename FunctionState>
-  static void TearDownFunctionState(FunctionState* function_state, Zone* zone) {
+  template <typename FunctionState>
+  static void TearDownFunctionState(FunctionState* function_state) {
     if (function_state->outer_function_state_ != NULL) {
-      zone->isolate()->set_ast_node_id(function_state->saved_ast_node_id_);
+      function_state->ast_node_id_gen_->set_id(
+          function_state->saved_ast_node_id_);
     }
   }