[stubs] Remove dead string copying code

src/arm/code-stubs-arm.h

Index: src/arm/code-stubs-arm.h
diff --git a/src/arm/code-stubs-arm.h b/src/arm/code-stubs-arm.h
index 30ae358eb05eae446c55040faf241e13b85d5346..6f1ad083c928f5b96cf7ec7d3c2b84f9b9d76ff6 100644
--- a/src/arm/code-stubs-arm.h
+++ b/src/arm/code-stubs-arm.h
@@ -16,17 +16,6 @@ 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,