Add support for debug break in Dart source.

runtime/vm/constants_arm64.h

 // Copyright (c) 2014, 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.
 
 #ifndef VM_CONSTANTS_ARM64_H_
 #define VM_CONSTANTS_ARM64_H_
 
 #include "platform/assert.h"
 
 namespace dart {
@@ skipping 781 matching lines @@
     kInstrSize = 4,
     kInstrSizeLog2 = 2,
     kPCReadOffset = 8
   };
 
   static const int32_t kNopInstruction = HINT;  // hint #0 === nop.
 
   // Reserved brk and hlt instruction codes.
   static const int32_t kBreakPointCode = 0xdeb0;  // For breakpoint.
   static const int32_t kStopMessageCode = 0xdeb1;  // For Stop(message).
-  static const int32_t kSimulatorMessageCode = 0xdeb2;  // For trace msg in sim.
-  static const int32_t kSimulatorBreakCode = 0xdeb3;  // For breakpoint in sim.
+  static const int32_t kSimulatorBreakCode = 0xdeb2;  // For breakpoint in sim.
   static const int32_t kSimulatorRedirectCode = 0xca11;  // For redirection.
 
   // Breakpoint instruction filling assembler code buffers in debug mode.
   static const int32_t kBreakPointInstruction =  // brk(0xdeb0).
       BRK | (kBreakPointCode << kImm16Shift);
 
   // Breakpoint instruction used by the simulator.
   // Should be distinct from kBreakPointInstruction and from a typical user
   // breakpoint inserted in generated code for debugging, e.g. brk(0).
   static const int32_t kSimulatorBreakpointInstruction =
@@ skipping 245 matching lines @@
   static Instr* At(uword pc) { return reinterpret_cast<Instr*>(pc); }
 
  private:
   DISALLOW_ALLOCATION();
   DISALLOW_IMPLICIT_CONSTRUCTORS(Instr);
 };
 
 }  // namespace dart
 
 #endif  // VM_CONSTANTS_ARM64_H_