Add X64 assembler.

runtime/vm/disassembler.cc

 // Copyright (c) 2011, 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/assembler.h"
 #include "vm/globals.h"
 #include "vm/os.h"
 
 namespace dart {
 
 void DisassembleToStdout::ConsumeInstruction(char* hex_buffer,
                                              intptr_t hex_size,
                                              char* human_buffer,
                                              intptr_t human_size,
                                              uword pc) {
-  static const int kHexColumnWidth = 18;
+  static const int kHexColumnWidth = 23;
   uint8_t* pc_ptr = reinterpret_cast<uint8_t*>(pc);
   OS::Print("%p    %s", pc_ptr, hex_buffer);
   int hex_length = strlen(hex_buffer);
   if (hex_length < kHexColumnWidth) {
     for (int i = kHexColumnWidth - hex_length; i > 0; i--) {
       OS::Print(" ");
     }
   }
   OS::Print("%s", human_buffer);
   OS::Print("\n");
 }
 
 
 void DisassembleToStdout::Print(const char* format, ...) {
   va_list args;
   va_start(args, format);
   OS::VFPrint(stdout, format, args);
   va_end(args);
 }
 
 }  // namespace dart