[for-in] Further refactorings and unification around for-in.

test/mjsunit/for-in-opt.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: --harmony-proxies --allow-natives-syntax --expose-debug-as debug
 
 "use strict";
 
 // Test non-JSObject receiver.
 function f(o) {
@@ skipping 49 matching lines @@
 
 function check_f2() {
   assertEquals(keys, f2(o));
   assertEquals(keys, has_keys);
   has_keys.length = 0;
 }
 
 check_f2();
 check_f2();
 
-// Test lazy deopt after GetPropertyNamesFast
+// Test lazy deopt after ForInEnumerate
 %OptimizeFunctionOnNextCall(f2);
 deopt_enum = true;
 check_f2();
 
 // Test lazy deopt after FILTER_KEY
 %OptimizeFunctionOnNextCall(f2);
 deopt_has = true;
 check_f2();
 
 function f3(o) {
@@ skipping 78 matching lines @@
 x = false;
 
 f5(); f5(); f5();
 %OptimizeFunctionOnNextCall(f5);
 x = true;
 count = 0;
 Debug.setListener(listener);
 f5();
 Debug.setListener(null);
 assertEquals(1, count);