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

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

 /*
  * Copyright (C) 2006, 2007, 2008 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 150 matching lines @@
   }
 
   if (CanWriteData())
     effect_allowed_ = effect;
 }
 
 void DataTransfer::clearData(const String& type) {
   if (!CanWriteData())
     return;
 
+  const size_t old_length = data_object_->length();
+
   if (type.IsNull())
     data_object_->ClearAll();
   else
     data_object_->ClearData(NormalizeType(type));
+
+  if (old_length != data_object_->length())
+    data_store_item_list_changed_ = true;
 }
 
 String DataTransfer::getData(const String& type) const {
   if (!CanReadData())
     return String();
 
   bool convert_to_url = false;
   String data = data_object_->GetData(NormalizeType(type, &convert_to_url));
   if (!convert_to_url)
     return data;
   return ConvertURIListToURL(data);
 }
 
 void DataTransfer::setData(const String& type, const String& data) {
   if (!CanWriteData())
     return;
 
   data_object_->SetData(NormalizeType(type), data);
+  data_store_item_list_changed_ = true;
 }
 
-// extensions beyond IE's API
-Vector<String> DataTransfer::types() const {
+bool DataTransfer::hasDataStoreItemListChanged() const {
+  return data_store_item_list_changed_ || !CanReadTypes();

[foolip, 2017/05/15 15:11:02]

Is there a test that would fail if the CanReadTypes() bit of this condition were
removed?

[Raphael Kubo da Costa (rakuco), 2017/05/15 15:17:59]

Yes; the previous iterations of this CL didn't have it, and were causing
SameSiteSubframe/DragAndDropBrowserTest.DragImageBetweenFrames/0 and 
CrossSiteSubframe/DragAndDropBrowserTest.DragImageBetweenFrames/0 (from
interactive_ui_tests) to fail because they were expecting "types" to return an
empty array on "dragend" events.

To be honest, I can't find anything on the spec saying types' behavior should
vary depending on the data store's mode but I found it safer to preserve that
part of the current behavior (ie. just because types returned a filled-in array
when the data store's mode was read-write doesn't mean the same array should be
returned when the data store's mode is set to "protected").

+}
+
+Vector<String> DataTransfer::types() {
   Vector<String> types;
   if (!CanReadTypes())
     return types;
 
+  data_store_item_list_changed_ = false;
   return data_object_->Types();
 }
 
 FileList* DataTransfer::files() const {
   FileList* files = FileList::Create();
   if (!CanReadData())
     return files;
 
   for (size_t i = 0; i < data_object_->length(); ++i) {
     if (data_object_->Item(i)->Kind() == DataObjectItem::kFileKind) {
@@ skipping 211 matching lines @@
   return data_object_;
 }
 
 DataTransfer::DataTransfer(DataTransferType type,
                            DataTransferAccessPolicy policy,
                            DataObject* data_object)
     : policy_(policy),
       drop_effect_("uninitialized"),
       effect_allowed_("uninitialized"),
       transfer_type_(type),
-      data_object_(data_object) {}
+      data_object_(data_object),
+      data_store_item_list_changed_(true) {}
 
 void DataTransfer::setDragImage(ImageResourceContent* image,
                                 Node* node,
                                 const IntPoint& loc) {
   if (!CanSetDragImage())
     return;
 
   drag_image_ = image;
   drag_loc_ = loc;
   drag_image_element_ = node;
@@ skipping 11 matching lines @@
         return true;
     }
   }
   return false;
 }
 
 bool DataTransfer::HasStringOfType(const String& type) const {
   if (!CanReadTypes())
     return false;
 
-  return types().Contains(type);
+  return data_object_->Types().Contains(type);
 }
 
 DragOperation ConvertDropZoneOperationToDragOperation(
     const String& drag_operation) {
   if (drag_operation == "copy")
     return kDragOperationCopy;
   if (drag_operation == "move")
     return kDragOperationMove;
   if (drag_operation == "link")
     return kDragOperationLink;
@@ skipping 13 matching lines @@
   }
 }
 
 DEFINE_TRACE(DataTransfer) {
   visitor->Trace(data_object_);
   visitor->Trace(drag_image_);
   visitor->Trace(drag_image_element_);
 }
 
 }  // namespace blink