[debugger] remove step count parameter from prepare step.

test/mjsunit/debug-stepframe-clearing.js

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Flags: --expose-debug-as debug
 
 // This test ensures that IC learning doesn't interfere with stepping into
 // property accessor. f1()'s ICs are allowed to learn to a monomorphic state,
 // and the breakpoints flooding get() are allowed to expire, then we ensure
 // that we can step into get() again later (when k == 1).
@@ skipping 30 matching lines @@
   try {
     var line = exec_state.frame(0).sourceLineText();
     print(line);
     var match = line.match(/\/\/ Break (\d+)$/);
     assertEquals(2, match.length);
     var match_value = parseInt(match[1]);
 
     if (break_count >= 0 && break_count < 2) {
       // 0, 1: Keep stepping through frames.
       assertEquals(break_count, match_value);
-      exec_state.prepareStep(Debug.StepAction.StepFrame, 1);
+      exec_state.prepareStep(Debug.StepAction.StepFrame);
     } else if (break_count === 2) {
       // 2: let the code run to a breakpoint we set. The load should
       // go monomorphic.
       assertEquals(break_count, match_value);
     } else if (break_count === 3) {
       // 3: back to frame stepping. Does the monomorphic slappy accessor
       // call still have the ability to break like before?
       assertEquals(break_count, match_value);
       Debug.clearBreakPoint(bp_f1_line7);
-      exec_state.prepareStep(Debug.StepAction.StepFrame, 1);
+      exec_state.prepareStep(Debug.StepAction.StepFrame);
     } else {
       assertEquals(4, break_count);
       assertEquals(2, match_value);
       // Apparently we can still stop in the accessor even though we cleared
       // breakpoints earlier and there was a monomorphic step.
       // Allow running to completion now.
       Debug.clearBreakPoint(bp_f1_line9);
     }
 
     break_count++;
@@ skipping 16 matching lines @@
   bp_f1_line7 = Debug.setBreakPoint(f1, 7);
   bp_f1_line9 = Debug.setBreakPoint(f1, 9);
 
   debugger;                         // Break 0
   f1();
   Debug.setListener(null);
   assertTrue(break_count === 5);
 }
 
 assertNull(exception);