Get rid of duplicated CPU::DebugBreak() method.

src/arm/cpu-arm.cc

 // Copyright 2006-2009 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 88 matching lines @@
         "bx  r3          \n\t"
         ".THUMB          \n"
     "2:                  \n\t"
         : "=r" (beg)
         : "0" (beg), "r" (end), "r" (flg), "r" (__ARM_NR_cacheflush)
         : "r3");
   #endif
 #endif
 }
 
-
-void CPU::DebugBreak() {
-#if !defined (__arm__)
-  UNIMPLEMENTED();  // when building ARM emulator target
-#else
-  asm volatile("bkpt 0");
-#endif
-}
-
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM