Introduce new stepping mode to step into another frame.

src/debug-debugger.js

 // Copyright 2012 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.
 
 // Default number of frames to include in the response to backtrace request.
 var kDefaultBacktraceLength = 10;
 
 var Debug = {};
 
 // Regular expression to skip "crud" at the beginning of a source line which is
@@ skipping 15 matching lines @@
 
 // Types of exceptions that can be broken upon.
 Debug.ExceptionBreak = { Caught : 0,
                          Uncaught: 1 };
 
 // The different types of steps.
 Debug.StepAction = { StepOut: 0,
                      StepNext: 1,
                      StepIn: 2,
                      StepMin: 3,
-                     StepInMin: 4 };
+                     StepInMin: 4,
+                     StepFrame: 5 };
 
 // The different types of scripts matching enum ScriptType in objects.h.
 Debug.ScriptType = { Native: 0,
                      Extension: 1,
                      Normal: 2 };
 
 // The different types of script compilations matching enum
 // Script::CompilationType in objects.h.
 Debug.ScriptCompilationType = { Host: 0,
                                 Eval: 1,
@@ skipping 2532 matching lines @@
 
     default:
       json = null;
   }
   return json;
 }
 
 Debug.TestApi = {
   CommandProcessorResolveValue: DebugCommandProcessor.resolveValue_
 };