[debugger] remove step count parameter from prepare step.

test/mjsunit/regress/regress-109195.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 14 matching lines @@
 // (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
 var Debug = debug.Debug;
 
 function listener(event, exec_state, event_data, data) {
   for (var i = 0, n = exec_state.frameCount(); i < n; i++) {
     exec_state.frame().scopeCount(i);
   }
-  exec_state.prepareStep(Debug.StepAction.Continue, 1);
+  exec_state.prepareStep(Debug.StepAction.StepNext);
 }
 
 Debug.setListener(listener);
 
 var F = function () {
   1, function () {
     var d = 0;
     (function () { d; });
     debugger;
   }();
@@ skipping 10 matching lines @@
 var G = function () {
   1, function () {
     var d = 0;
     (function () { d; });
     debugger;
   }['f'];
 };
 
 var src = "(" + G.toString() + ")()";
 eval(src);