[debugger] remove step count parameter from prepare step.

test/mjsunit/debug-stepin-function-call.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 20 matching lines @@
 
 var exception = null;
 var state = 0;
 
 // Simple debug event handler which first time will cause 'step in' action
 // to get into g.call and than check that execution is pauesed inside
 // function 'g'.
 function listener(event, exec_state, event_data, data) {
   try {
     if (event == Debug.DebugEvent.Break) {
-      if (state == 0) {
+      if (state < 2) {
         // Step into f2.call:
-        exec_state.prepareStep(Debug.StepAction.StepIn, 2);
-        state = 2;
-      } else if (state == 2) {
+        exec_state.prepareStep(Debug.StepAction.StepIn);
+        state++;
+      } else {
         assertEquals('g', event_data.func().name());
         assertEquals('  return t + 1; // expected line',
                      event_data.sourceLineText());
         state = 3;
       }
     }
   } catch(e) {
     exception = e;
   }
 };
@@ skipping 110 matching lines @@
 // Test global bound function.
 state = 0;
 var globalBound = g.bind(null, 3);
 debugger;
 globalBound();
 assertNull(exception);
 assertEquals(3, state);
 
 // Get rid of the debug event listener.
 Debug.setListener(null);