Add support for debug break in Dart source.

runtime/vm/ast.h

 // Copyright (c) 2012, 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_AST_H_
 #define VM_AST_H_
 
 #include "platform/assert.h"
 #include "vm/allocation.h"
 #include "vm/growable_array.h"
@@ skipping 16 matching lines @@
   V(Comparison)                                                                \
   V(UnaryOp)                                                                   \
   V(ConditionalExpr)                                                           \
   V(If)                                                                        \
   V(Switch)                                                                    \
   V(Case)                                                                      \
   V(While)                                                                     \
   V(DoWhile)                                                                   \
   V(For)                                                                       \
   V(Jump)                                                                      \
+  V(Stop)                                                                      \
   V(ArgumentList)                                                              \
   V(Array)                                                                     \
   V(Closure)                                                                   \
   V(InstanceCall)                                                              \
   V(StaticCall)                                                                \
   V(ClosureCall)                                                               \
   V(CloneContext)                                                              \
   V(ConstructorCall)                                                           \
   V(InstanceGetter)                                                            \
   V(InstanceSetter)                                                            \
@@ skipping 1089 matching lines @@
 
  private:
   Token::Kind kind_;
   SourceLabel* label_;
   GrowableArray<InlinedFinallyNode*> inlined_finally_list_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(JumpNode);
 };
 
 
+class StopNode : public AstNode {
+ public:
+  StopNode(intptr_t token_pos, const char* message)
+      : AstNode(token_pos),
+        message_(message) {
+    ASSERT(message != NULL);
+  }
+
+  const char* message() const { return message_; }
+
+  virtual void VisitChildren(AstNodeVisitor* visitor) const { }
+
+  DECLARE_COMMON_NODE_FUNCTIONS(StopNode);
+
+ private:
+  const char* message_;
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(StopNode);
+};
+
+
 class LoadLocalNode : public AstNode {
  public:
   LoadLocalNode(intptr_t token_pos, const LocalVariable* local)
       : AstNode(token_pos), local_(*local) {
     ASSERT(local != NULL);
   }
 
   const LocalVariable& local() const { return local_; }
 
   virtual void VisitChildren(AstNodeVisitor* visitor) const { }
@@ skipping 784 matching lines @@
   const intptr_t try_index_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(InlinedFinallyNode);
 };
 
 }  // namespace dart
 
 #undef DECLARE_COMMON_NODE_FUNCTIONS
 
 #endif  // VM_AST_H_