Remove the obsolete OverwriteMode optimization.

src/full-codegen.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_FULL_CODEGEN_H_
 #define V8_FULL_CODEGEN_H_
 
 #include "src/v8.h"
 
 #include "src/allocation.h"
@@ skipping 566 matching lines @@
   // Adds the properties to the class (function) object and to its prototype.
   // Expects the class (function) in the accumulator. The class (function) is
   // in the accumulator after installing all the properties.
   void EmitClassDefineProperties(ClassLiteral* lit);
 
   // Pushes the property key as a Name on the stack.
   void EmitPropertyKey(ObjectLiteralProperty* property, BailoutId bailout_id);
 
   // Apply the compound assignment operator. Expects the left operand on top
   // of the stack and the right one in the accumulator.
-  void EmitBinaryOp(BinaryOperation* expr,
-                    Token::Value op,
-                    OverwriteMode mode);
+  void EmitBinaryOp(BinaryOperation* expr, Token::Value op);
 
   // Helper functions for generating inlined smi code for certain
   // binary operations.
   void EmitInlineSmiBinaryOp(BinaryOperation* expr,
                              Token::Value op,
-                             OverwriteMode mode,
                              Expression* left,
                              Expression* right);
 
   // Assign to the given expression as if via '='. The right-hand-side value
   // is expected in the accumulator.
   void EmitAssignment(Expression* expr);
 
   // Shall an error be thrown if assignment with 'op' operation is perfomed
   // on this variable in given language mode?
   static bool IsSignallingAssignmentToConst(Variable* var, Token::Value op,
@@ skipping 444 matching lines @@
 
   Address start_;
   Address instruction_start_;
   uint32_t length_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_FULL_CODEGEN_H_