[debugger] fix break locations for assignments and return.

src/debug/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_DEBUG_H_
 #define V8_DEBUG_DEBUG_H_
 
 #include "src/allocation.h"
 #include "src/arguments.h"
 #include "src/assembler.h"
@@ skipping 124 matching lines @@
       while (count-- > 0) Next();
     }
 
     virtual int code_offset() = 0;
     int break_index() const { return break_index_; }
     inline int position() const { return position_; }
     inline int statement_position() const { return statement_position_; }
 
    protected:
     explicit Iterator(Handle<DebugInfo> debug_info);
+    int ReturnPosition();
 
     Handle<DebugInfo> debug_info_;
     int break_index_;
     int position_;
     int statement_position_;
 
    private:
     DisallowHeapAllocation no_gc_;
     DISALLOW_COPY_AND_ASSIGN(Iterator);
   };
@@ skipping 638 matching lines @@
                                   Handle<Code> code);
   static bool DebugBreakSlotIsPatched(Address pc);
   static void ClearDebugBreakSlot(Isolate* isolate, Address pc);
 };
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_DEBUG_DEBUG_H_