[debugger] remove step count parameter from prepare step.

test/mjsunit/debug-continue.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 56 matching lines @@
 
 function listener(event, exec_state, event_data, data) {
   try {
   if (event == Debug.DebugEvent.Break) {
 
     // Test simple continue request.
     testArguments(exec_state, void 0, true);
 
     // Test some illegal continue requests.
     testArguments(exec_state, '{"stepaction":"maybe"}', false);
-    testArguments(exec_state, '{"stepcount":-1}', false);
 
     // Test some legal continue requests.
     testArguments(exec_state, '{"stepaction":"in"}', true);
     testArguments(exec_state, '{"stepaction":"next"}', true);
     testArguments(exec_state, '{"stepaction":"out"}', true);
+
+    // Step count argument is ignored.
+    testArguments(exec_state, '{"stepcount":-1}', true);
     testArguments(exec_state, '{"stepcount":1}', true);
     testArguments(exec_state, '{"stepcount":10}', true);
     testArguments(exec_state, '{"stepcount":"10"}', true);
     testArguments(exec_state, '{"stepaction":"next","stepcount":10}', true);
 
     // Indicate that all was processed.
     listenerComplete = true;
   }
   } catch (e) {
     exception = e
@@ skipping 11 matching lines @@
   f();
 };
 
 // Set a break point and call to invoke the debug event listener.
 Debug.setBreakPoint(g, 0, 0);
 g();
 
 assertFalse(exception, "exception in listener")
 // Make sure that the debug event listener vas invoked.
 assertTrue(listenerComplete, "listener did not run to completion");