Fix several little buglets with stepping

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_debugger_api.h"
 
 #include "vm/object.h"
@@ skipping 304 matching lines @@
 
   void VisitObjectPointers(ObjectPointerVisitor* visitor);
 
   // Called from Runtime when a breakpoint in Dart code is reached.
   void BreakpointCallback();
 
   // Returns true if there is at least one breakpoint set in func.
   // Checks for both user-defined and internal temporary breakpoints.
   bool HasBreakpoint(const Function& func);
 
+  // Returns true if the call at address pc is patched to point to
+  // a debugger stub.
+  bool HasActiveBreakpoint(uword pc);
+
   // Returns a stack trace with frames corresponding to invisible functions
   // omitted. CurrentStackTrace always returns a new trace on the current stack.
   // The trace returned by StackTrace may have been cached; it is suitable for
   // use when stepping, but otherwise may be out of sync with the current stack.
   DebuggerStackTrace* StackTrace();
   DebuggerStackTrace* CurrentStackTrace();
 
   // Returns a debugger stack trace corresponding to a dart.core.Stacktrace.
   // Frames corresponding to invisible functions are omitted. It is not valid
   // to query local variables in the returned stack.
@@ skipping 137 matching lines @@
 
   friend class Isolate;
   friend class SourceBreakpoint;
   DISALLOW_COPY_AND_ASSIGN(Debugger);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_DEBUGGER_H_