Add support for debug break in Dart source.

runtime/vm/ast_printer.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/ast_printer.h"
 
 #include "vm/handles.h"
 #include "vm/log.h"
 #include "vm/object.h"
 #include "vm/os.h"
@@ skipping 409 matching lines @@
   }
   ISL_Print(")");
 }
 
 
 void AstPrinter::VisitThrowNode(ThrowNode* node) {
   VisitGenericAstNode(node);
 }
 
 
+void AstPrinter::VisitStopNode(StopNode* node) {
+  ISL_Print("(%s %s)", node->PrettyName(), node->message());
+}
+
+
 void AstPrinter::VisitInlinedFinallyNode(InlinedFinallyNode* node) {
   VisitGenericAstNode(node);
 }
 
 
 void AstPrinter::PrintNode(AstNode* node) {
   ASSERT(node != NULL);
   AstPrinter ast_printer;
   node->Visit(&ast_printer);
   ISL_Print("\n");
@@ skipping 120 matching lines @@
   ASSERT(node_sequence != NULL);
   AstPrinter ast_printer;
   const char* function_name =
       parsed_function.function().ToFullyQualifiedCString();
   ISL_Print("Ast for function '%s' {\n", function_name);
   node_sequence->Visit(&ast_printer);
   ISL_Print("}\n");
 }
 
 }  // namespace dart