Revert of [intl] Remove redundant type checking system

src/i18n.cc

Index: src/i18n.cc
diff --git a/src/i18n.cc b/src/i18n.cc
index bb7423c845a2a2bed4ccb2b1fb6053e7d247714f..58b8a8dc5c7a5d9df902b01201763df958fd5a3c 100644
--- a/src/i18n.cc
+++ b/src/i18n.cc
@@ -759,7 +759,16 @@
 icu::SimpleDateFormat* DateFormat::UnpackDateFormat(
     Isolate* isolate,
     Handle<JSObject> obj) {
-  return reinterpret_cast<icu::SimpleDateFormat*>(obj->GetInternalField(0));
+  Handle<String> key =
+      isolate->factory()->NewStringFromStaticChars("dateFormat");
+  Maybe<bool> maybe = JSReceiver::HasOwnProperty(obj, key);
+  CHECK(maybe.IsJust());
+  if (maybe.FromJust()) {
+    return reinterpret_cast<icu::SimpleDateFormat*>(
+        obj->GetInternalField(0));
+  }
+
+  return NULL;
 }
 
 void DateFormat::DeleteDateFormat(const v8::WeakCallbackInfo<void>& data) {
@@ -814,7 +823,15 @@
 icu::DecimalFormat* NumberFormat::UnpackNumberFormat(
     Isolate* isolate,
     Handle<JSObject> obj) {
-  return reinterpret_cast<icu::DecimalFormat*>(obj->GetInternalField(0));
+  Handle<String> key =
+      isolate->factory()->NewStringFromStaticChars("numberFormat");
+  Maybe<bool> maybe = JSReceiver::HasOwnProperty(obj, key);
+  CHECK(maybe.IsJust());
+  if (maybe.FromJust()) {
+    return reinterpret_cast<icu::DecimalFormat*>(obj->GetInternalField(0));
+  }
+
+  return NULL;
 }
 
 void NumberFormat::DeleteNumberFormat(const v8::WeakCallbackInfo<void>& data) {
@@ -866,7 +883,14 @@
 
 icu::Collator* Collator::UnpackCollator(Isolate* isolate,
                                         Handle<JSObject> obj) {
-  return reinterpret_cast<icu::Collator*>(obj->GetInternalField(0));
+  Handle<String> key = isolate->factory()->NewStringFromStaticChars("collator");
+  Maybe<bool> maybe = JSReceiver::HasOwnProperty(obj, key);
+  CHECK(maybe.IsJust());
+  if (maybe.FromJust()) {
+    return reinterpret_cast<icu::Collator*>(obj->GetInternalField(0));
+  }
+
+  return NULL;
 }
 
 void Collator::DeleteCollator(const v8::WeakCallbackInfo<void>& data) {
@@ -921,7 +945,15 @@
 
 icu::BreakIterator* BreakIterator::UnpackBreakIterator(Isolate* isolate,
                                                        Handle<JSObject> obj) {
-  return reinterpret_cast<icu::BreakIterator*>(obj->GetInternalField(0));
+  Handle<String> key =
+      isolate->factory()->NewStringFromStaticChars("breakIterator");
+  Maybe<bool> maybe = JSReceiver::HasOwnProperty(obj, key);
+  CHECK(maybe.IsJust());
+  if (maybe.FromJust()) {
+    return reinterpret_cast<icu::BreakIterator*>(obj->GetInternalField(0));
+  }
+
+  return NULL;
 }
 
 void BreakIterator::DeleteBreakIterator(