Fix a bug where breakpoints where not getting properly deleted.

runtime/vm/debugger.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_DEBUGGER_H_
 #define VM_DEBUGGER_H_
 
 #include "include/dart_tools_api.h"
 
 #include "vm/object.h"
@@ skipping 633 matching lines @@
 
   void CollectLibraryFields(const GrowableObjectArray& field_list,
                             const Library& lib,
                             const String& prefix,
                             bool include_private_fields);
 
   // Handles any events which pause vm execution.  Breakpoints,
   // interrupts, etc.
   void Pause(DebuggerEvent* event);
 
-  void HandleSteppingRequest(DebuggerStackTrace* stack_trace);
+  void HandleSteppingRequest(DebuggerStackTrace* stack_trace,
+                             bool skip_next_step = false);
 
   Isolate* isolate_;
   Dart_Port isolate_id_;  // A unique ID for the isolate in the debugger.
   bool initialized_;
   bool creation_message_sent_;  // The creation message has been sent.
 
   // ID number generator.
   intptr_t next_id_;
 
   BreakpointLocation* latent_locations_;
@@ skipping 18 matching lines @@
   RemoteObjectCache* obj_cache_;
 
   // Current stack trace. Valid only while IsPaused().
   DebuggerStackTrace* stack_trace_;
 
   // When stepping through code, only pause the program if the top
   // frame corresponds to this fp value, or if the top frame is
   // lower on the stack.
   uword stepping_fp_;
 
+  // If we step while at a breakpoint, we would hit the same pc twice.
+  // We use this field to let us skip the next single-step after a
+  // breakpoint.
+  bool skip_next_step_;
+
   Dart_ExceptionPauseInfo exc_pause_info_;
 
   static EventHandler* event_handler_;
 
   friend class Isolate;
   friend class BreakpointLocation;
   DISALLOW_COPY_AND_ASSIGN(Debugger);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_DEBUGGER_H_