Strict mode arguments do not share binding with formal parameters.

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 1655 matching lines @@
                   Scope* scope,
                   ZoneList<Statement*>* body,
                   int materialized_literal_count,
                   int expected_property_count,
                   bool has_only_simple_this_property_assignments,
                   Handle<FixedArray> this_property_assignments,
                   int num_parameters,
                   int start_position,
                   int end_position,
                   bool is_expression,
-                  bool contains_loops,
-                  bool strict_mode)
+                  bool contains_loops)
       : name_(name),
         scope_(scope),
         body_(body),
         materialized_literal_count_(materialized_literal_count),
         expected_property_count_(expected_property_count),
         has_only_simple_this_property_assignments_(
             has_only_simple_this_property_assignments),
         this_property_assignments_(this_property_assignments),
         num_parameters_(num_parameters),
         start_position_(start_position),
         end_position_(end_position),
         is_expression_(is_expression),
         contains_loops_(contains_loops),
-        strict_mode_(strict_mode),
         function_token_position_(RelocInfo::kNoPosition),
         inferred_name_(Heap::empty_string()),
         try_full_codegen_(false),
         pretenure_(false) { }
 
   DECLARE_NODE_TYPE(FunctionLiteral)
 
   Handle<String> name() const { return name_; }
   Scope* scope() const { return scope_; }
   ZoneList<Statement*>* body() const { return body_; }
   void set_function_token_position(int pos) { function_token_position_ = pos; }
   int function_token_position() const { return function_token_position_; }
   int start_position() const { return start_position_; }
   int end_position() const { return end_position_; }
   bool is_expression() const { return is_expression_; }
   bool contains_loops() const { return contains_loops_; }
-  bool strict_mode() const { return strict_mode_; }
+  bool strict_mode() const;
 
   int materialized_literal_count() { return materialized_literal_count_; }
   int expected_property_count() { return expected_property_count_; }
   bool has_only_simple_this_property_assignments() {
       return has_only_simple_this_property_assignments_;
   }
   Handle<FixedArray> this_property_assignments() {
       return this_property_assignments_;
   }
   int num_parameters() { return num_parameters_; }
@@ skipping 449 matching lines @@
   AST_NODE_LIST(DEF_VISIT)
 #undef DEF_VISIT
 
  private:
   bool stack_overflow_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_AST_H_