Use a breakpoint instruction for a stop message on arm instead of

runtime/vm/disassembler_arm64.cc

Index: runtime/vm/disassembler_arm64.cc
===================================================================
--- runtime/vm/disassembler_arm64.cc	(revision 45360)
+++ runtime/vm/disassembler_arm64.cc	(working copy)
@@ -829,6 +829,14 @@
   } else if ((instr->Bits(0, 2) == 0) && (instr->Bits(2, 3) == 0) &&
              (instr->Bits(21, 3) == 1)) {
     Format(instr, "brk 'imm16");
+    if (instr->Imm16Field() == Instr::kStopMessageCode) {
+      const char* message = *reinterpret_cast<const char**>(
+          reinterpret_cast<intptr_t>(instr) - 2 * Instr::kInstrSize);
+      buffer_pos_ += OS::SNPrint(current_position_in_buffer(),
+                                 remaining_size_in_buffer(),
+                                 " ; \"%s\"",
+                                 message);
+    }
   } else if ((instr->Bits(0, 2) == 0) && (instr->Bits(2, 3) == 0) &&
              (instr->Bits(21, 3) == 2)) {
     Format(instr, "hlt 'imm16");