Clean up Isolate usages in ast visitor and hydrogen.

src/ast.h

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2162 matching lines @@
   static RegExpEmpty kInstance;
 };
 
 
 // ----------------------------------------------------------------------------
 // Basic visitor
 // - leaf node visitors are abstract.
 
 class AstVisitor BASE_EMBEDDED {
  public:
-  AstVisitor() : stack_overflow_(false) { }
+  AstVisitor() : isolate_(Isolate::Current()), stack_overflow_(false) { }
   virtual ~AstVisitor() { }
 
   // Stack overflow check and dynamic dispatch.
   void Visit(AstNode* node) { if (!CheckStackOverflow()) node->Accept(this); }
 
   // Iteration left-to-right.
   virtual void VisitDeclarations(ZoneList<Declaration*>* declarations);
   virtual void VisitStatements(ZoneList<Statement*>* statements);
   virtual void VisitExpressions(ZoneList<Expression*>* expressions);
 
   // Stack overflow tracking support.
   bool HasStackOverflow() const { return stack_overflow_; }
   bool CheckStackOverflow();
 
   // If a stack-overflow exception is encountered when visiting a
   // node, calling SetStackOverflow will make sure that the visitor
   // bails out without visiting more nodes.
   void SetStackOverflow() { stack_overflow_ = true; }
   void ClearStackOverflow() { stack_overflow_ = false; }
 
   // Nodes not appearing in the AST, including slots.
   virtual void VisitSlot(Slot* node) { UNREACHABLE(); }
 
   // Individual AST nodes.
 #define DEF_VISIT(type)                         \
   virtual void Visit##type(type* node) = 0;
   AST_NODE_LIST(DEF_VISIT)
 #undef DEF_VISIT
 
+ protected:
+  Isolate* isolate() { return isolate_; }
+
  private:
+  Isolate* isolate_;
   bool stack_overflow_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_AST_H_