[debugger] simplify stepping logic.

src/runtime/runtime-debug.cc

 // Copyright 2014 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.
 
 #include "src/runtime/runtime-utils.h"
 
 #include "src/arguments.h"
 #include "src/debug/debug.h"
 #include "src/debug/debug-evaluate.h"
 #include "src/debug/debug-frames.h"
@@ skipping 1213 matching lines @@
   StepAction step_action = static_cast<StepAction>(NumberToInt32(args[1]));
   if (step_action != StepIn && step_action != StepNext &&
       step_action != StepOut && step_action != StepFrame) {
     return isolate->Throw(isolate->heap()->illegal_argument_string());
   }
 
   // Clear all current stepping setup.
   isolate->debug()->ClearStepping();
 
   // Prepare step.
-  isolate->debug()->PrepareStep(static_cast<StepAction>(step_action), 1);
+  isolate->debug()->PrepareStep(static_cast<StepAction>(step_action));
   return isolate->heap()->undefined_value();
 }
 
 
 // Clear all stepping set by PrepareStep.
 RUNTIME_FUNCTION(Runtime_ClearStepping) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 0);
   RUNTIME_ASSERT(isolate->debug()->is_active());
   isolate->debug()->ClearStepping();
@@ skipping 435 matching lines @@
   return Smi::FromInt(isolate->debug()->is_active());
 }
 
 
 RUNTIME_FUNCTION(Runtime_DebugBreakInOptimizedCode) {
   UNIMPLEMENTED();
   return NULL;
 }
 }  // namespace internal
 }  // namespace v8