Provide list of step-in source positions in JS Debug API

src/debug.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 79 matching lines @@
   void Next();
   void Next(int count);
   void FindBreakLocationFromAddress(Address pc);
   void FindBreakLocationFromPosition(int position);
   void Reset();
   bool Done() const;
   void SetBreakPoint(Handle<Object> break_point_object);
   void ClearBreakPoint(Handle<Object> break_point_object);
   void SetOneShot();
   void ClearOneShot();
+  bool IsStepInLocation(Isolate* isolate);
   void PrepareStepIn(Isolate* isolate);
   bool IsExit() const;
   bool HasBreakPoint();
   bool IsDebugBreak();
   Object* BreakPointObjects();
   void ClearAllDebugBreak();
 
 
   inline int code_position() {
     return static_cast<int>(pc() - debug_info_->code()->entry());
@@ skipping 939 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(MessageDispatchHelperThread);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // ENABLE_DEBUGGER_SUPPORT
 
 #endif  // V8_DEBUG_H_