Eliminate a potential warning about extra format arguments.

runtime/vm/disassembler_x64.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/disassembler.h"
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_IA32.
 #if defined(TARGET_ARCH_X64)
 #include "platform/utils.h"
 #include "vm/allocation.h"
@@ skipping 1540 matching lines @@
             break;
           case 4:
             mnem = "jmp";
             break;
           case 6:
             mnem = "push";
             break;
           default:
             mnem = "???";
         }
-        AppendToBuffer(((regop <= 1) ? "%s%c " : "%s "),
-                       mnem,
-                       operand_size_code());
+        if (regop <= 1) {
+          AppendToBuffer("%s%c ", mnem, operand_size_code());
+        } else {
+          AppendToBuffer("%s ", mnem);
+        }
         data += PrintRightOperand(data);
       }
         break;
 
       case 0xC7:  // imm32, fall through
       case 0xC6:  // imm8
       {
         bool is_byte = *data == 0xC6;
         data++;
         if (is_byte) {
@@ skipping 282 matching lines @@
                                   human_buffer,
                                   sizeof(human_buffer),
                                   pc);
     pc += instruction_length;
   }
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64