Fix GC-unsafe use of BreakLocationIterator.

src/debug.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_DEBUG_H_
 #define V8_DEBUG_H_
 
 #include "src/allocation.h"
 #include "src/arguments.h"
 #include "src/assembler.h"
@@ skipping 68 matching lines @@
   void FindBreakLocationFromAddress(Address pc);
   void FindBreakLocationFromPosition(int position,
       BreakPositionAlignment alignment);
   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 667 matching lines @@
   // several frames above.
   // There is no calling conventions here, because it never actually gets
   // called, it only gets returned to.
   static void GenerateFrameDropperLiveEdit(MacroAssembler* masm);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_DEBUG_H_