Changed the debugger API to allow only one debug event listener to be registe...

test/mjsunit/debug-event-listener.js

 // Copyright 2008 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 24 matching lines @@
   if (event == Debug.DebugEvent.Break ||
       event == Debug.DebugEvent.Exception)
   {
     lastDebugEvent.event = event;
     lastDebugEvent.frameFuncName = exec_state.frame().func().name();
     lastDebugEvent.event_data = event_data;
   }
 };
 
 // Add the debug event listener.
-Debug.addListener(listener);
+Debug.setListener(listener);
 // Get events from handled exceptions.
 Debug.setBreakOnException();
 
 // Test debug event for handled exception.
 (function f(){
   try {
     x();
   } catch(e) {
     // Do nothing. Ignore exception.
   }
 })();
 assertTrue(lastDebugEvent.event == Debug.DebugEvent.Exception);
 assertEquals(lastDebugEvent.frameFuncName, "f");
 assertFalse(lastDebugEvent.event_data.uncaught());
 Debug.clearBreakOnException();
 
 // Test debug event for break point.
 function a() {
   x = 1;
   y = 2;
   z = 3;
 };
 Debug.setBreakPoint(a, 1);
 a();
 assertTrue(lastDebugEvent.event == Debug.DebugEvent.Break);
 assertEquals(lastDebugEvent.frameFuncName, "a");
 
-Debug.removeListener(listener);
+Debug.setListener(null);