[debugger] fix stepping out of across throwing.

test/mjsunit/regress/regress-5559.js

-// Copyright 2015 the V8 project authors. All rights reserved.
+// Copyright 2016 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
 
 Debug = debug.Debug
 
 var exception = null;
 var break_count = 0;
 
 function listener(event, exec_state, event_data, data) {
   if (event != Debug.DebugEvent.Break) return;
   try {
     print(event_data.sourceLineText());
     assertTrue(
         event_data.sourceLineText().indexOf(`Break ${break_count++}.`) > 0);
-    exec_state.prepareStep(Debug.StepAction.StepIn);
+    exec_state.prepareStep(Debug.StepAction.StepFrame);

[jgruber, 2016/10/25 07:28:54]

StepOut as discussed offline.

   } catch (e) {
     exception = e;
   }
 };
 
-function customSplit() {
-  return "x";              // Break 2.
-}                          // Break 3.
-var o = {};
-o[Symbol.split] = customSplit;
+function thrower() {
+  try {
+    debugger;             // Break 0.
+    throw 'error';
+  } catch (err) {
+  }
+}
+
 
 Debug.setListener(listener);
-debugger;                  // Break 0.
-var result = "".split(o);  // Break 1.
-Debug.setListener(null);   // Break 4.
+thrower();
+Debug.setListener(null);  // Break 1.
 
-assertEquals("x", result);
 assertNull(exception);

[jgruber, 2016/10/25 07:28:54]

Should we assertEquals(2, break_count) here?