[debugger] debug-evaluate should not not modify local values.

test/mjsunit/debug-evaluate-locals-capturing.js

 // 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.
 
-// Flags: --expose-debug-as debug
+// Flags: --expose-debug-as debug --debug-eval-readonly-locals
 
 Debug = debug.Debug
 var exception = null;
 var break_count = 0;
 
 var f = null;
 var i = null;
 function listener(event, exec_state, event_data, data) {
   try {
     if (event == Debug.DebugEvent.Break) {
       var frameMirror = exec_state.frame(0);
 
-      f = frameMirror.evaluate('f = function() { i = 5; }, f(), f').value();
-      print(f);
+      var i = frameMirror.evaluate('f = function() { i = 5; }, f(), i').value();
+      assertEquals(5, i);
     }
   } catch(e) {
     exception = e;
     print(e, e.stack);
   }
 };
 
 Debug.setListener(listener);
 
 (function (){
 
   var i = 0;
 
   try {
     throw new Error();
   } catch (e) {
     assertEquals(0, i);
     debugger;
-    assertEquals(5, i);
+    assertEquals(0, i);
   }
 }());
 
 assertNull(exception);
 
 assertNull(i);
 f();
 assertNull(i);
 
 Debug.setListener(null);