Add basic crankshaft support for slow-mode for-in to avoid disabling optimizations

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
+
+"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) {
+    if (deopt_enum) {
+      %DeoptimizeFunction(f2);
+      deopt_enum = false;
+    }
+    return keys;
+  },
+
+  getPropertyDescriptor: function(k) {
+    if (deopt_has) {
+      %DeoptimizeFunction(f2);
+      deopt_has = false;
+    }
+    has_keys.push(k);
+    return {value: 10, configurable: true, writable: false, enumerable: true};
+  }
+};
+
+
+var proxy = Proxy.create(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();