Add support for debug break in Dart source.

runtime/vm/ast_transformer.cc

 // 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.
 
 #include "vm/ast_transformer.h"
 
 #include "vm/object_store.h"
 #include "vm/parser.h"
 #include "vm/thread.h"
 
 namespace dart {
 
 // Quick access to the current zone.
 #define Z (thread()->zone())
 
 // Nodes that are unreachable from already parsed expressions.
 #define FOR_EACH_UNREACHABLE_NODE(V)                                           \
   V(AwaitMarker)                                                               \
   V(Case)                                                                      \
   V(CatchClause)                                                               \
   V(CloneContext)                                                              \
   V(ClosureCall)                                                               \
   V(DoWhile)                                                                   \
   V(If)                                                                        \
   V(InitStaticField)                                                           \
   V(InlinedFinally)                                                            \
   V(For)                                                                       \
   V(Jump)                                                                      \
+  V(Stop)                                                                      \
   V(LoadInstanceField)                                                         \
   V(NativeBody)                                                                \
   V(Primary)                                                                   \
   V(Return)                                                                    \
   V(Sequence)                                                                  \
   V(StoreInstanceField)                                                        \
   V(Switch)                                                                    \
   V(TryCatch)                                                                  \
   V(While)
 
@@ skipping 564 matching lines @@
 
 
 void AwaitTransformer::VisitThrowNode(ThrowNode* node) {
   AstNode* new_exception = Transform(node->exception());
   result_ = new(Z) ThrowNode(node->token_pos(),
                              new_exception,
                              node->stacktrace());
 }
 
 }  // namespace dart