[proxy] fixing harmony/proxy.js tests and improving error messages + some drive-by fixes

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) {
   var result = [];
   for (var i in o) {
     result.push(i);
   }
   return result;
 }
 
 assertEquals(["0"], f("a"));
 assertEquals(["0"], f("a"));
+
 %OptimizeFunctionOnNextCall(f);
 assertEquals(["0","1","2"], f("bla"));
 
 // Test the lazy deopt points.
 var keys = ["a", "b", "c", "d"];
 var has_keys = [];
 var deopt_has = false;
 var deopt_enum = false;
 
 var handler = {
-  enumerate: function(target) {
+  enumerate(target) {
     if (deopt_enum) {
       %DeoptimizeFunction(f2);
       deopt_enum = false;
     }
-    return keys;
+    return keys[Symbol.iterator]();
   },
 
-  getPropertyDescriptor: function(k) {
+  has(target, k) {
     if (deopt_has) {
       %DeoptimizeFunction(f2);
       deopt_has = false;
     }
     has_keys.push(k);
     return {value: 10, configurable: true, writable: false, enumerable: true};
   }
 };
 
 
 var proxy = new Proxy({}, handler);
 var o = {__proto__: proxy};
 
 function f2(o) {
   var result = [];
   for (var i in o) {
     result.push(i);
   }
   return result;
 }
 
 function check_f2() {
   assertEquals(keys, f2(o));
   assertEquals(keys, has_keys);
   has_keys.length = 0;
 }
 
 check_f2();
 check_f2();
+
 // Test lazy deopt after GetPropertyNamesFast
 %OptimizeFunctionOnNextCall(f2);
 deopt_enum = true;
 check_f2();
+
 // Test lazy deopt after FILTER_KEY
 %OptimizeFunctionOnNextCall(f2);
 deopt_has = true;
 check_f2();
 
 function f3(o) {
   for (var i in o) {
   }
 }
 
 f3({__proto__:{x:1}});
 f3({__proto__:{x:1}});
+
 %OptimizeFunctionOnNextCall(f3);
 f3(undefined);
 f3(null);
 
 // Reliable repro for an issue previously flushed out by GC stress.
 var handler2 = {
-  getPropertyDescriptor: function(k) {
+  getPropertyDescriptor(target, k) {
     has_keys.push(k);
     return {value: 10, configurable: true, writable: false, enumerable: true};
   }
 }
 var proxy2 = new Proxy({}, handler2);
 var o2 = {__proto__: proxy2};
 var p = {x: "x"}
 
 function f4(o, p) {
   var result = [];
   for (var i in o) {
     var j = p.x + "str";
     result.push(i);
   }
   return result;
 }
+
 function check_f4() {
   assertEquals(keys, f4(o, p));
   assertEquals(keys, has_keys);
   has_keys.length = 0;
 }
+
 check_f4();
 check_f4();
+
 %OptimizeFunctionOnNextCall(f4);
+
 p.y = "y";  // Change map, cause eager deopt.
 check_f4();
 
 // Repro for Turbofan equivalent.
 var x;
 var count = 0;
 
 var Debug = debug.Debug;
 
 function listener(event, exec_state, event_data, data) {
   if (event == Debug.DebugEvent.Break) {
     %DeoptimizeFunction(f5);
   }
 }
 
 var handler3 = {
-  enumerate: function(target) {
-    return ["a", "b"];
+  enumerate(target) {
+    return ["a", "b"][Symbol.iterator]();
   },
 
-  getPropertyDescriptor: function(k) {
+  has(target, k) {
     if (k == "a") count++;
     if (x) %ScheduleBreak();
     return {value: 10, configurable: true, writable: false, enumerable: true};
   }
 };
 
 var proxy3 = new Proxy({}, handler3);
 var o3 = {__proto__: proxy3};
 
 function f5() {
   for (var p in o3) {
     print(p);
   }
 }
 
 x = false;
 
 f5(); f5(); f5();
 %OptimizeFunctionOnNextCall(f5);
 x = true;
 count = 0;
 Debug.setListener(listener);
 f5();
 Debug.setListener(null);
 assertEquals(1, count);