A64: Fix compilation with clang

src/a64/macro-assembler-a64.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2148 matching lines @@
 };
 
 
 // Use this scope when you need a one-to-one mapping bewteen methods and
 // instructions. This scope prevents the MacroAssembler from being called and
 // literal pools from being emitted. It also asserts the number of instructions
 // emitted is what you specified when creating the scope.
 class InstructionAccurateScope BASE_EMBEDDED {
  public:
   InstructionAccurateScope(MacroAssembler* masm, size_t count = 0)
-      : masm_(masm), size_(count * kInstructionSize) {
+      : masm_(masm)
+#ifdef DEBUG
+        ,
+        size_(count * kInstructionSize)
+#endif
+  {
     masm_->StartBlockConstPool();
 #ifdef DEBUG
     if (count != 0) {
       masm_->bind(&start_);
     }
     previous_allow_macro_instructions_ = masm_->allow_macro_instructions();
     masm_->set_allow_macro_instructions(false);
 #endif
   }
 
   ~InstructionAccurateScope() {
     masm_->EndBlockConstPool();
 #ifdef DEBUG
     if (start_.is_bound()) {
       ASSERT(masm_->SizeOfCodeGeneratedSince(&start_) == size_);
     }
     masm_->set_allow_macro_instructions(previous_allow_macro_instructions_);
 #endif
   }
 
  private:
   MacroAssembler* masm_;
+#ifdef DEBUG
   size_t size_;
-#ifdef DEBUG
   Label start_;
   bool previous_allow_macro_instructions_;
 #endif
 };
 
 
 inline MemOperand ContextMemOperand(Register context, int index) {
   return MemOperand(context, Context::SlotOffset(index));
 }
 
@@ skipping 56 matching lines @@
 #error "Unsupported option"
 #define CODE_COVERAGE_STRINGIFY(x) #x
 #define CODE_COVERAGE_TOSTRING(x) CODE_COVERAGE_STRINGIFY(x)
 #define __FILE_LINE__ __FILE__ ":" CODE_COVERAGE_TOSTRING(__LINE__)
 #define ACCESS_MASM(masm) masm->stop(__FILE_LINE__); masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 #endif  // V8_A64_MACRO_ASSEMBLER_A64_H_