[stubs] Remove dead string copying code

src/s390/code-stubs-s390.h

 // Copyright 2014 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_S390_CODE_STUBS_S390_H_
 #define V8_S390_CODE_STUBS_S390_H_
 
 #include "src/s390/frames-s390.h"
 
 namespace v8 {
 namespace internal {
 
 void ArrayNativeCode(MacroAssembler* masm, Label* call_generic_code);
 
 class StringHelper : public AllStatic {
  public:
-  // Generate code for copying a large number of characters. This function
-  // is allowed to spend extra time setting up conditions to make copying
-  // faster. Copying of overlapping regions is not supported.
-  // Dest register ends at the position after the last character written.
-  static void GenerateCopyCharacters(MacroAssembler* masm, Register dest,
-                                     Register src, Register count,
-                                     Register scratch,
-                                     String::Encoding encoding);
-
   // Compares two flat one-byte strings and returns result in r0.
   static void GenerateCompareFlatOneByteStrings(MacroAssembler* masm,
                                                 Register left, Register right,
                                                 Register scratch1,
                                                 Register scratch2,
                                                 Register scratch3);
 
   // Compares two flat one-byte strings for equality and returns result in r0.
   static void GenerateFlatOneByteStringEquals(MacroAssembler* masm,
                                               Register left, Register right,
@@ skipping 422 matching lines @@
   static void LoadNumber(MacroAssembler* masm, Register object,
                          DoubleRegister dst, Register heap_number_map,
                          Register scratch1, Register scratch2,
                          Label* not_number);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_S390_CODE_STUBS_S390_H_