[Interpreter] Add support for for..in.

src/runtime/runtime-interpreter.cc

Index: src/runtime/runtime-interpreter.cc
diff --git a/src/runtime/runtime-interpreter.cc b/src/runtime/runtime-interpreter.cc
index 96ebe5d4d3f48cfe77ab1239e8ef0c530a1a213d..ef86869ccce92d1a73e2ff5ca71f8eb337e1668d 100644
--- a/src/runtime/runtime-interpreter.cc
+++ b/src/runtime/runtime-interpreter.cc
@@ -147,5 +147,53 @@ RUNTIME_FUNCTION(Runtime_InterpreterNewClosure) {
       shared, context, static_cast<PretenureFlag>(pretenured_flag));
 }
 
+
+RUNTIME_FUNCTION(Runtime_InterpreterForInPrepare) {
+  HandleScope scope(isolate);
+  DCHECK_EQ(2, args.length());
+  CONVERT_ARG_HANDLE_CHECKED(JSReceiver, receiver, 0);
+  CONVERT_ARG_HANDLE_CHECKED(HeapObject, property_names, 1);
+
+  Handle<Object> cache_type = property_names;
+  Handle<Map> cache_type_map = handle(property_names->map(), isolate);
+  Handle<Map> receiver_map = handle(receiver->map(), isolate);
+
+  Handle<FixedArray> cache_array;
+  int cache_length;
+
+  if (cache_type_map.is_identical_to(isolate->factory()->meta_map())) {
+    int enum_length = cache_type_map->EnumLength();
+    DescriptorArray* descriptors = receiver_map->instance_descriptors();
+    if (enum_length > 0 && descriptors->HasEnumCache()) {
+      cache_array = handle(descriptors->GetEnumCache(), isolate);
+      cache_length = cache_array->length();
+    } else {
+      cache_array = isolate->factory()->empty_fixed_array();
+      cache_length = 0;
+    }
+  } else {
+    cache_array = Handle<FixedArray>::cast(cache_type);
+    cache_length = cache_array->length();
+
+    STATIC_ASSERT(FIRST_JS_PROXY_TYPE == FIRST_SPEC_OBJECT_TYPE);
+    if (receiver_map->instance_type() <= LAST_JS_PROXY_TYPE) {
+      DCHECK_GE(receiver_map->instance_type(), LAST_JS_PROXY_TYPE);
+      // Zero indicates proxy
+      cache_type = Handle<Object>(Smi::FromInt(0), isolate);
+    } else {
+      // One entails slow check
+      cache_type = Handle<Object>(Smi::FromInt(1), isolate);
+    }
+  }
+
+  Handle<FixedArray> result = isolate->factory()->NewFixedArray(4);
+  result->set(0, *receiver);
+  result->set(1, *cache_array);
+  result->set(2, *cache_type);
+  result->set(3, Smi::FromInt(cache_length));
+  return *result;
+}
+
+
 }  // namespace internal
 }  // namespace v8