[debugger] add utility to print break location.

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 599 matching lines @@
   MaybeHandle<Object> CallFunction(const char* name, int argc,
                                    Handle<Object> args[]);
 
   inline void AssertDebugContext() {
     DCHECK(isolate_->context() == *debug_context());
     DCHECK(in_debug_scope());
   }
 
   void ThreadInit();
 
+  void PrintBreakLocation();
+
   // Global handles.
   Handle<Context> debug_context_;
   Handle<Object> event_listener_;
   Handle<Object> event_listener_data_;
 
   v8::Debug::MessageHandler message_handler_;
 
   static const int kQueueInitialSize = 4;
   base::Semaphore command_received_;  // Signaled for each command received.
   LockingCommandMessageQueue command_queue_;
@@ skipping 161 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_