Introduce some predicates over variable modes.

src/ast.h

 // Copyright 2012 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 436 matching lines @@
   virtual InitializationFlag initialization() const = 0;
   virtual bool IsInlineable() const;
 
  protected:
   Declaration(VariableProxy* proxy,
               VariableMode mode,
               Scope* scope)
       : proxy_(proxy),
         mode_(mode),
         scope_(scope) {
-    ASSERT(mode == VAR ||
-           mode == CONST ||
-           mode == CONST_HARMONY ||
-           mode == LET);
+    ASSERT(IsDeclaredVariableMode(mode));
   }
 
  private:
   VariableProxy* proxy_;
   VariableMode mode_;
 
   // Nested scope from which the declaration originated.
   Scope* scope_;
 };
 
@@ skipping 2534 matching lines @@
  private:
   Isolate* isolate_;
   Zone* zone_;
   Visitor visitor_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_AST_H_