[cleanup] Delete MacroAssembler::CopyBytes, it is dead code

src/mips64/macro-assembler-mips64.h

Index: src/mips64/macro-assembler-mips64.h
diff --git a/src/mips64/macro-assembler-mips64.h b/src/mips64/macro-assembler-mips64.h
index b622a6008162243ff93e65e49e581ee473ce0250..65c90bec312a21da5326907adcfa92272f3c7c92 100644
--- a/src/mips64/macro-assembler-mips64.h
+++ b/src/mips64/macro-assembler-mips64.h
@@ -1190,14 +1190,6 @@ class MacroAssembler: public Assembler {
   // Must preserve the result register.
   void PopStackHandler();
 
-  // Copies a number of bytes from src to dst. All registers are clobbered. On
-  // exit src and dst will point to the place just after where the last byte was
-  // read or written and length will be zero.
-  void CopyBytes(Register src,
-                 Register dst,
-                 Register length,
-                 Register scratch);
-
   // Initialize fields with filler values.  Fields starting at |current_address|
   // not including |end_address| are overwritten with the value in |filler|.  At
   // the end the loop, |current_address| takes the value of |end_address|.