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

test/mjsunit/debug-liveedit-stack-padding.js

 // Copyright 2012 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 11 matching lines @@
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // Flags: --expose-debug-as debug
 // Get the Debug object exposed from the debug context global object.
 
 Debug = debug.Debug;
+Debug.setListener(listener);
 
 SlimFunction = eval(
     "(function() {\n " +
     "  return 'Cat';\n" +
     "})\n"
 );
 
 var script = Debug.findScript(SlimFunction);
 
 Debug.setScriptBreakPointById(script.id, 1, 0);
@@ skipping 27 matching lines @@
     try {
       debugger_handler();
     } catch (e) {
       saved_exception = e;
     }
   } else {
     print("Other: " + event);
   }
 }
 
-Debug.setListener(listener);
 
 var animal = SlimFunction();
 
 if (saved_exception) {
   print("Exception: " + saved_exception);
   assertUnreachable();
 }
 
 assertEquals("Capybara", animal);
+
+Debug.setListener(null);