DataTransfer: Make |types| be a FrozenArray<DOMString>.

third_party/WebKit/Source/core/clipboard/DataObject.cpp

 /*
  * Copyright (c) 2008, 2009, 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 72 matching lines @@
 DataObjectItem* DataObject::Item(unsigned long index) {
   if (index >= length())
     return nullptr;
   return item_list_[index];
 }
 
 void DataObject::DeleteItem(unsigned long index) {
   if (index >= length())
     return;
   item_list_.erase(index);
+  NotifyItemListChanged();
 }
 
 void DataObject::ClearAll() {
+  if (item_list_.IsEmpty())
+    return;
   item_list_.clear();
+  NotifyItemListChanged();
 }
 
 DataObjectItem* DataObject::Add(const String& data, const String& type) {
   DataObjectItem* item = DataObjectItem::CreateFromString(type, data);
   if (!InternalAddStringItem(item))
     return nullptr;
   return item;
 }
 
 DataObjectItem* DataObject::Add(File* file) {
@@ skipping 14 matching lines @@
   InternalAddFileItem(item);
   return item;
 }
 
 void DataObject::ClearData(const String& type) {
   for (size_t i = 0; i < item_list_.size(); ++i) {
     if (item_list_[i]->Kind() == DataObjectItem::kStringKind &&
         item_list_[i]->GetType() == type) {
       // Per the spec, type must be unique among all items of kind 'string'.
       item_list_.erase(i);
+      NotifyItemListChanged();
       return;
     }
   }
 }
 
 Vector<String> DataObject::Types() const {
   Vector<String> results;
 #if DCHECK_IS_ON()
   HashSet<String> types_seen;
 #endif
@@ skipping 108 matching lines @@
 
 bool DataObject::InternalAddStringItem(DataObjectItem* item) {
   DCHECK_EQ(item->Kind(), DataObjectItem::kStringKind);
   for (size_t i = 0; i < item_list_.size(); ++i) {
     if (item_list_[i]->Kind() == DataObjectItem::kStringKind &&
         item_list_[i]->GetType() == item->GetType())
       return false;
   }
 
   item_list_.push_back(item);
+  NotifyItemListChanged();
   return true;
 }
 
 void DataObject::InternalAddFileItem(DataObjectItem* item) {
   DCHECK_EQ(item->Kind(), DataObjectItem::kFileKind);
   item_list_.push_back(item);
+  NotifyItemListChanged();
+}
+
+void DataObject::AddObserver(Observer* observer) {
+  DCHECK(!observers_.Contains(observer));
+  observers_.insert(observer);
+}
+
+void DataObject::NotifyItemListChanged() const {
+  for (const auto& observer : observers_)
+    observer->OnItemListChanged();
 }
 
 DEFINE_TRACE(DataObject) {
   visitor->Trace(item_list_);
+  visitor->Trace(observers_);
   Supplementable<DataObject>::Trace(visitor);
 }
 
 DataObject* DataObject::Create(WebDragData data) {
   DataObject* data_object = Create();
   bool has_file_system = false;
 
   WebVector<WebDragData::Item> items = data.Items();
   for (unsigned i = 0; i < items.size(); ++i) {
     WebDragData::Item item = items[i];
@@ skipping 90 matching lines @@
     } else {
       NOTREACHED();
     }
     item_list[i] = item;
   }
   data.SwapItems(item_list);
   return data;
 }
 
 }  // namespace blink