[stubs] Remove dead string copying code

src/x87/code-stubs-x87.h

Index: src/x87/code-stubs-x87.h
diff --git a/src/x87/code-stubs-x87.h b/src/x87/code-stubs-x87.h
index 6290cfed1c3827e84a34d5de618fa744ef11928e..a5c7563d295dfc4d14e27777f46cfb283cdc440e 100644
--- a/src/x87/code-stubs-x87.h
+++ b/src/x87/code-stubs-x87.h
@@ -16,16 +16,6 @@ void ArrayNativeCode(MacroAssembler* masm,
 
 class StringHelper : public AllStatic {
  public:
-  // Generate code for copying characters using the rep movs instruction.
-  // Copies ecx characters from esi to edi. Copying of overlapping regions is
-  // not supported.
-  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 eax.
   static void GenerateCompareFlatOneByteStrings(MacroAssembler* masm,
                                                 Register left, Register right,