Debugger: require debugger to be active when dealing with breaks.

test/mjsunit/debug-script.js

Index: test/mjsunit/debug-script.js
diff --git a/test/mjsunit/debug-script.js b/test/mjsunit/debug-script.js
index b3047de8fa7c8836daf4e354117025ac401ee310..32415c24287b2264a5b5f678a523e76bbc49d2a8 100644
--- a/test/mjsunit/debug-script.js
+++ b/test/mjsunit/debug-script.js
@@ -36,6 +36,7 @@
 
 // Get the Debug object exposed from the debug context global object.
 Debug = debug.Debug;
+Debug.setListener(function(){});
 
 Date();
 RegExp();
@@ -103,3 +104,5 @@ assertEquals(Debug.ScriptType.Normal, debug_script.type);
 // Check a nonexistent script.
 var dummy_script = Debug.findScript('dummy.js');
 assertTrue(typeof dummy_script == 'undefined');
+
+Debug.setListener(null);