Add m-esr52 at 52.6.0

1 files changed, 1565 insertions, 0 deletions

diff --git a/dom/events/DataTransfer.cpp b/dom/events/DataTransfer.cpp
new file mode 100644
index 000000000..2c6ecdd56
--- /dev/null
+++ b/dom/events/DataTransfer.cpp
@@ -0,0 +1,1565 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/BasicEvents.h"
+
+#include "DataTransfer.h"
+
+#include "nsIDOMDocument.h"
+#include "nsISupportsPrimitives.h"
+#include "nsIScriptSecurityManager.h"
+#include "mozilla/dom/DOMStringList.h"
+#include "nsArray.h"
+#include "nsError.h"
+#include "nsIDragService.h"
+#include "nsIClipboard.h"
+#include "nsContentUtils.h"
+#include "nsIContent.h"
+#include "nsIBinaryInputStream.h"
+#include "nsIBinaryOutputStream.h"
+#include "nsIStorageStream.h"
+#include "nsStringStream.h"
+#include "nsCRT.h"
+#include "nsIScriptObjectPrincipal.h"
+#include "nsIScriptContext.h"
+#include "nsIDocument.h"
+#include "nsIScriptGlobalObject.h"
+#include "nsVariant.h"
+#include "mozilla/dom/ContentChild.h"
+#include "mozilla/dom/DataTransferBinding.h"
+#include "mozilla/dom/DataTransferItemList.h"
+#include "mozilla/dom/Directory.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/FileList.h"
+#include "mozilla/dom/BindingUtils.h"
+#include "mozilla/dom/OSFileSystem.h"
+#include "mozilla/dom/Promise.h"
+#include "nsNetUtil.h"
+
+namespace mozilla {
+namespace dom {
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(DataTransfer)
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(DataTransfer)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mParent)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mItems)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mDragTarget)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mDragImage)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_PRESERVED_WRAPPER
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(DataTransfer)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mParent)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mItems)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mDragTarget)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mDragImage)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+NS_IMPL_CYCLE_COLLECTION_TRACE_WRAPPERCACHE(DataTransfer)
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(DataTransfer)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(DataTransfer)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(DataTransfer)
+  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
+  NS_INTERFACE_MAP_ENTRY(mozilla::dom::DataTransfer)
+  NS_INTERFACE_MAP_ENTRY(nsIDOMDataTransfer)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIDOMDataTransfer)
+NS_INTERFACE_MAP_END
+
+// the size of the array
+const char DataTransfer::sEffects[8][9] = {
+  "none", "copy", "move", "copyMove", "link", "copyLink", "linkMove", "all"
+};
+
+// Used for custom clipboard types.
+enum CustomClipboardTypeId {
+  eCustomClipboardTypeId_None,
+  eCustomClipboardTypeId_String
+};
+
+DataTransfer::DataTransfer(nsISupports* aParent, EventMessage aEventMessage,
+                           bool aIsExternal, int32_t aClipboardType)
+  : mParent(aParent)
+  , mDropEffect(nsIDragService::DRAGDROP_ACTION_NONE)
+  , mEffectAllowed(nsIDragService::DRAGDROP_ACTION_UNINITIALIZED)
+  , mEventMessage(aEventMessage)
+  , mCursorState(false)
+  , mReadOnly(true)
+  , mIsExternal(aIsExternal)
+  , mUserCancelled(false)
+  , mIsCrossDomainSubFrameDrop(false)
+  , mClipboardType(aClipboardType)
+  , mDragImageX(0)
+  , mDragImageY(0)
+{
+  mItems = new DataTransferItemList(this, aIsExternal);
+  // For these events, we want to be able to add data to the data transfer, so
+  // clear the readonly state. Otherwise, the data is already present. For
+  // external usage, cache the data from the native clipboard or drag.
+  if (aEventMessage == eCut ||
+      aEventMessage == eCopy ||
+      aEventMessage == eDragStart) {
+    mReadOnly = false;
+  } else if (mIsExternal) {
+    if (aEventMessage == ePaste) {
+      CacheExternalClipboardFormats();
+    } else if (aEventMessage >= eDragDropEventFirst &&
+               aEventMessage <= eDragDropEventLast) {
+      CacheExternalDragFormats();
+    }
+  }
+}
+
+DataTransfer::DataTransfer(nsISupports* aParent,
+                           EventMessage aEventMessage,
+                           const uint32_t aEffectAllowed,
+                           bool aCursorState,
+                           bool aIsExternal,
+                           bool aUserCancelled,
+                           bool aIsCrossDomainSubFrameDrop,
+                           int32_t aClipboardType,
+                           DataTransferItemList* aItems,
+                           Element* aDragImage,
+                           uint32_t aDragImageX,
+                           uint32_t aDragImageY)
+  : mParent(aParent)
+  , mDropEffect(nsIDragService::DRAGDROP_ACTION_NONE)
+  , mEffectAllowed(aEffectAllowed)
+  , mEventMessage(aEventMessage)
+  , mCursorState(aCursorState)
+  , mReadOnly(true)
+  , mIsExternal(aIsExternal)
+  , mUserCancelled(aUserCancelled)
+  , mIsCrossDomainSubFrameDrop(aIsCrossDomainSubFrameDrop)
+  , mClipboardType(aClipboardType)
+  , mDragImage(aDragImage)
+  , mDragImageX(aDragImageX)
+  , mDragImageY(aDragImageY)
+{
+  MOZ_ASSERT(mParent);
+  MOZ_ASSERT(aItems);
+
+  // We clone the items array after everything else, so that it has a valid
+  // mParent value
+  mItems = aItems->Clone(this);
+  // The items are copied from aItems into mItems. There is no need to copy
+  // the actual data in the items as the data transfer will be read only. The
+  // dragstart event is the only time when items are
+  // modifiable, but those events should have been using the first constructor
+  // above.
+  NS_ASSERTION(aEventMessage != eDragStart,
+               "invalid event type for DataTransfer constructor");
+}
+
+DataTransfer::~DataTransfer()
+{}
+
+// static
+already_AddRefed<DataTransfer>
+DataTransfer::Constructor(const GlobalObject& aGlobal,
+                          const nsAString& aEventType, bool aIsExternal,
+                          ErrorResult& aRv)
+{
+  nsAutoCString onEventType("on");
+  AppendUTF16toUTF8(aEventType, onEventType);
+  nsCOMPtr<nsIAtom> eventTypeAtom = NS_Atomize(onEventType);
+  if (!eventTypeAtom) {
+    aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
+    return nullptr;
+  }
+
+  EventMessage eventMessage = nsContentUtils::GetEventMessage(eventTypeAtom);
+  RefPtr<DataTransfer> transfer = new DataTransfer(aGlobal.GetAsSupports(),
+                                                     eventMessage, aIsExternal,
+                                                     -1);
+  return transfer.forget();
+}
+
+JSObject*
+DataTransfer::WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto)
+{
+  return DataTransferBinding::Wrap(aCx, this, aGivenProto);
+}
+
+NS_IMETHODIMP
+DataTransfer::GetDropEffect(nsAString& aDropEffect)
+{
+  nsString dropEffect;
+  GetDropEffect(dropEffect);
+  aDropEffect = dropEffect;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DataTransfer::SetDropEffect(const nsAString& aDropEffect)
+{
+  // the drop effect can only be 'none', 'copy', 'move' or 'link'.
+  for (uint32_t e = 0; e <= nsIDragService::DRAGDROP_ACTION_LINK; e++) {
+    if (aDropEffect.EqualsASCII(sEffects[e])) {
+      // don't allow copyMove
+      if (e != (nsIDragService::DRAGDROP_ACTION_COPY |
+                nsIDragService::DRAGDROP_ACTION_MOVE)) {
+        mDropEffect = e;
+      }
+      break;
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DataTransfer::GetEffectAllowed(nsAString& aEffectAllowed)
+{
+  nsString effectAllowed;
+  GetEffectAllowed(effectAllowed);
+  aEffectAllowed = effectAllowed;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DataTransfer::SetEffectAllowed(const nsAString& aEffectAllowed)
+{
+  if (aEffectAllowed.EqualsLiteral("uninitialized")) {
+    mEffectAllowed = nsIDragService::DRAGDROP_ACTION_UNINITIALIZED;
+    return NS_OK;
+  }
+
+  static_assert(nsIDragService::DRAGDROP_ACTION_NONE == 0,
+                "DRAGDROP_ACTION_NONE constant is wrong");
+  static_assert(nsIDragService::DRAGDROP_ACTION_COPY == 1,
+                "DRAGDROP_ACTION_COPY constant is wrong");
+  static_assert(nsIDragService::DRAGDROP_ACTION_MOVE == 2,
+                "DRAGDROP_ACTION_MOVE constant is wrong");
+  static_assert(nsIDragService::DRAGDROP_ACTION_LINK == 4,
+                "DRAGDROP_ACTION_LINK constant is wrong");
+
+  for (uint32_t e = 0; e < ArrayLength(sEffects); e++) {
+    if (aEffectAllowed.EqualsASCII(sEffects[e])) {
+      mEffectAllowed = e;
+      break;
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DataTransfer::GetDropEffectInt(uint32_t* aDropEffect)
+{
+  *aDropEffect = mDropEffect;
+  return  NS_OK;
+}
+
+NS_IMETHODIMP
+DataTransfer::SetDropEffectInt(uint32_t aDropEffect)
+{
+  mDropEffect = aDropEffect;
+  return  NS_OK;
+}
+
+NS_IMETHODIMP
+DataTransfer::GetEffectAllowedInt(uint32_t* aEffectAllowed)
+{
+  *aEffectAllowed = mEffectAllowed;
+  return  NS_OK;
+}
+
+NS_IMETHODIMP
+DataTransfer::SetEffectAllowedInt(uint32_t aEffectAllowed)
+{
+  mEffectAllowed = aEffectAllowed;
+  return  NS_OK;
+}
+
+NS_IMETHODIMP
+DataTransfer::GetMozUserCancelled(bool* aUserCancelled)
+{
+  *aUserCancelled = MozUserCancelled();
+  return NS_OK;
+}
+
+already_AddRefed<FileList>
+DataTransfer::GetFiles(nsIPrincipal& aSubjectPrincipal,
+                       ErrorResult& aRv)
+{
+  return mItems->Files(&aSubjectPrincipal);
+}
+
+NS_IMETHODIMP
+DataTransfer::GetFiles(nsIDOMFileList** aFileList)
+{
+  if (!aFileList) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // The XPCOM interface is only avaliable to system code, and thus we can
+  // assume the system principal. This is consistent with the previous behavour
+  // of this function, which also assumed the system principal.
+  //
+  // This code is also called from C++ code, which expects it to have a System
+  // Principal, and thus the SubjectPrincipal cannot be used.
+  RefPtr<FileList> files = mItems->Files(nsContentUtils::GetSystemPrincipal());
+
+  files.forget(aFileList);
+  return NS_OK;
+}
+
+void
+DataTransfer::GetTypes(nsTArray<nsString>& aTypes,
+                       nsIPrincipal& aSubjectPrincipal) const
+{
+  // When called from bindings, aTypes will be empty, but since we might have
+  // Gecko-internal callers too, clear it to be safe.
+  aTypes.Clear();
+  
+  const nsTArray<RefPtr<DataTransferItem>>* items = mItems->MozItemsAt(0);
+  if (NS_WARN_IF(!items)) {
+    return;
+  }
+
+  for (uint32_t i = 0; i < items->Length(); i++) {
+    DataTransferItem* item = items->ElementAt(i);
+    MOZ_ASSERT(item);
+
+    if (item->ChromeOnly() && !nsContentUtils::IsSystemPrincipal(&aSubjectPrincipal)) {
+      continue;
+    }
+
+    // NOTE: The reason why we get the internal type here is because we want
+    // kFileMime to appear in the types list for backwards compatibility
+    // reasons.
+    nsAutoString type;
+    item->GetInternalType(type);
+    if (item->Kind() == DataTransferItem::KIND_STRING || type.EqualsASCII(kFileMime)) {
+      // If the entry has kind KIND_STRING, we want to add it to the list.
+      aTypes.AppendElement(type);
+    }
+  }
+
+  for (uint32_t i = 0; i < mItems->Length(); ++i) {
+    bool found = false;
+    DataTransferItem* item = mItems->IndexedGetter(i, found);
+    MOZ_ASSERT(found);
+    if (item->Kind() != DataTransferItem::KIND_FILE) {
+      continue;
+    }
+    aTypes.AppendElement(NS_LITERAL_STRING("Files"));
+    break;
+  }
+}
+
+void
+DataTransfer::GetData(const nsAString& aFormat, nsAString& aData,
+                      nsIPrincipal& aSubjectPrincipal,
+                      ErrorResult& aRv)
+{
+  // return an empty string if data for the format was not found
+  aData.Truncate();
+
+  nsCOMPtr<nsIVariant> data;
+  nsresult rv =
+    GetDataAtInternal(aFormat, 0, &aSubjectPrincipal,
+                      getter_AddRefs(data));
+  if (NS_FAILED(rv)) {
+    if (rv != NS_ERROR_DOM_INDEX_SIZE_ERR) {
+      aRv.Throw(rv);
+    }
+    return;
+  }
+
+  if (data) {
+    nsAutoString stringdata;
+    data->GetAsAString(stringdata);
+
+    // for the URL type, parse out the first URI from the list. The URIs are
+    // separated by newlines
+    nsAutoString lowercaseFormat;
+    nsContentUtils::ASCIIToLower(aFormat, lowercaseFormat);
+
+    if (lowercaseFormat.EqualsLiteral("url")) {
+      int32_t lastidx = 0, idx;
+      int32_t length = stringdata.Length();
+      while (lastidx < length) {
+        idx = stringdata.FindChar('\n', lastidx);
+        // lines beginning with # are comments
+        if (stringdata[lastidx] == '#') {
+          if (idx == -1) {
+            break;
+          }
+        }
+        else {
+          if (idx == -1) {
+            aData.Assign(Substring(stringdata, lastidx));
+          } else {
+            aData.Assign(Substring(stringdata, lastidx, idx - lastidx));
+          }
+          aData = nsContentUtils::TrimWhitespace<nsCRT::IsAsciiSpace>(aData,
+                                                                      true);
+          return;
+        }
+        lastidx = idx + 1;
+      }
+    }
+    else {
+      aData = stringdata;
+    }
+  }
+}
+
+void
+DataTransfer::SetData(const nsAString& aFormat, const nsAString& aData,
+                      nsIPrincipal& aSubjectPrincipal,
+                      ErrorResult& aRv)
+{
+  RefPtr<nsVariantCC> variant = new nsVariantCC();
+  variant->SetAsAString(aData);
+
+  aRv = SetDataAtInternal(aFormat, variant, 0, &aSubjectPrincipal);
+}
+
+void
+DataTransfer::ClearData(const Optional<nsAString>& aFormat,
+                        nsIPrincipal& aSubjectPrincipal,
+                        ErrorResult& aRv)
+{
+  if (mReadOnly) {
+    aRv.Throw(NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR);
+    return;
+  }
+
+  if (MozItemCount() == 0) {
+    return;
+  }
+
+  if (aFormat.WasPassed()) {
+    MozClearDataAtHelper(aFormat.Value(), 0, aSubjectPrincipal, aRv);
+  } else {
+    MozClearDataAtHelper(EmptyString(), 0, aSubjectPrincipal, aRv);
+  }
+}
+
+NS_IMETHODIMP
+DataTransfer::GetMozItemCount(uint32_t* aCount)
+{
+  *aCount = MozItemCount();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DataTransfer::GetMozCursor(nsAString& aCursorState)
+{
+  nsString cursor;
+  GetMozCursor(cursor);
+  aCursorState = cursor;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DataTransfer::SetMozCursor(const nsAString& aCursorState)
+{
+  // Lock the cursor to an arrow during the drag.
+  mCursorState = aCursorState.EqualsLiteral("default");
+
+  return NS_OK;
+}
+
+already_AddRefed<nsINode>
+DataTransfer::GetMozSourceNode()
+{
+  nsCOMPtr<nsIDragSession> dragSession = nsContentUtils::GetDragSession();
+  if (!dragSession) {
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIDOMNode> sourceNode;
+  dragSession->GetSourceNode(getter_AddRefs(sourceNode));
+  nsCOMPtr<nsINode> node = do_QueryInterface(sourceNode);
+  if (node && !nsContentUtils::LegacyIsCallerNativeCode()
+      && !nsContentUtils::CanCallerAccess(node)) {
+    return nullptr;
+  }
+
+  return node.forget();
+}
+
+NS_IMETHODIMP
+DataTransfer::GetMozSourceNode(nsIDOMNode** aSourceNode)
+{
+  nsCOMPtr<nsINode> sourceNode = GetMozSourceNode();
+  if (!sourceNode) {
+    *aSourceNode = nullptr;
+    return NS_OK;
+  }
+
+  return CallQueryInterface(sourceNode, aSourceNode);
+}
+
+already_AddRefed<DOMStringList>
+DataTransfer::MozTypesAt(uint32_t aIndex, ErrorResult& aRv) const
+{
+  // Only the first item is valid for clipboard events
+  if (aIndex > 0 &&
+      (mEventMessage == eCut || mEventMessage == eCopy ||
+       mEventMessage == ePaste)) {
+    aRv.Throw(NS_ERROR_DOM_INDEX_SIZE_ERR);
+    return nullptr;
+  }
+
+  RefPtr<DOMStringList> types = new DOMStringList();
+  if (aIndex < MozItemCount()) {
+    // note that you can retrieve the types regardless of their principal
+    const nsTArray<RefPtr<DataTransferItem>>& items = *mItems->MozItemsAt(aIndex);
+
+    bool addFile = false;
+    for (uint32_t i = 0; i < items.Length(); i++) {
+      if (items[i]->ChromeOnly() && !nsContentUtils::LegacyIsCallerChromeOrNativeCode()) {
+        continue;
+      }
+
+      // NOTE: The reason why we get the internal type here is because we want
+      // kFileMime to appear in the types list for backwards compatibility
+      // reasons.
+      nsAutoString type;
+      items[i]->GetInternalType(type);
+      if (NS_WARN_IF(!types->Add(type))) {
+        aRv.Throw(NS_ERROR_FAILURE);
+        return nullptr;
+      }
+
+      if (items[i]->Kind() == DataTransferItem::KIND_FILE) {
+        addFile = true;
+      }
+    }
+
+    if (addFile) {
+      types->Add(NS_LITERAL_STRING("Files"));
+    }
+  }
+
+  return types.forget();
+}
+
+NS_IMETHODIMP
+DataTransfer::MozTypesAt(uint32_t aIndex, nsISupports** aTypes)
+{
+  ErrorResult rv;
+  RefPtr<DOMStringList> types = MozTypesAt(aIndex, rv);
+  types.forget(aTypes);
+  return rv.StealNSResult();
+}
+
+nsresult
+DataTransfer::GetDataAtNoSecurityCheck(const nsAString& aFormat,
+                                       uint32_t aIndex,
+                                       nsIVariant** aData)
+{
+  return GetDataAtInternal(aFormat, aIndex,
+                           nsContentUtils::GetSystemPrincipal(), aData);
+}
+
+nsresult
+DataTransfer::GetDataAtInternal(const nsAString& aFormat, uint32_t aIndex,
+                                nsIPrincipal* aSubjectPrincipal,
+                                nsIVariant** aData)
+{
+  *aData = nullptr;
+
+  if (aFormat.IsEmpty()) {
+    return NS_OK;
+  }
+
+  if (aIndex >= MozItemCount()) {
+    return NS_ERROR_DOM_INDEX_SIZE_ERR;
+  }
+
+  // Only the first item is valid for clipboard events
+  if (aIndex > 0 &&
+      (mEventMessage == eCut || mEventMessage == eCopy ||
+       mEventMessage == ePaste)) {
+    return NS_ERROR_DOM_INDEX_SIZE_ERR;
+  }
+
+  nsAutoString format;
+  GetRealFormat(aFormat, format);
+
+  MOZ_ASSERT(aSubjectPrincipal);
+
+  RefPtr<DataTransferItem> item = mItems->MozItemByTypeAt(format, aIndex);
+  if (!item) {
+    // The index exists but there's no data for the specified format, in this
+    // case we just return undefined
+    return NS_OK;
+  }
+
+  // If we have chrome only content, and we aren't chrome, don't allow access
+  if (!nsContentUtils::IsSystemPrincipal(aSubjectPrincipal) && item->ChromeOnly()) {
+    return NS_OK;
+  }
+
+  // DataTransferItem::Data() handles the principal checks
+  ErrorResult result;
+  nsCOMPtr<nsIVariant> data = item->Data(aSubjectPrincipal, result);
+  if (NS_WARN_IF(!data || result.Failed())) {
+    return result.StealNSResult();
+  }
+
+  data.forget(aData);
+  return NS_OK;
+}
+
+void
+DataTransfer::MozGetDataAt(JSContext* aCx, const nsAString& aFormat,
+                           uint32_t aIndex,
+                           JS::MutableHandle<JS::Value> aRetval,
+                           nsIPrincipal& aSubjectPrincipal,
+                           mozilla::ErrorResult& aRv)
+{
+  nsCOMPtr<nsIVariant> data;
+  aRv = GetDataAtInternal(aFormat, aIndex, &aSubjectPrincipal,
+                          getter_AddRefs(data));
+  if (aRv.Failed()) {
+    return;
+  }
+
+  if (!data) {
+    aRetval.setNull();
+    return;
+  }
+
+  JS::Rooted<JS::Value> result(aCx);
+  if (!VariantToJsval(aCx, data, aRetval)) {
+    aRv = NS_ERROR_FAILURE;
+    return;
+  }
+}
+
+/* static */ bool
+DataTransfer::PrincipalMaySetData(const nsAString& aType,
+                                  nsIVariant* aData,
+                                  nsIPrincipal* aPrincipal)
+{
+  if (!nsContentUtils::IsSystemPrincipal(aPrincipal)) {
+    DataTransferItem::eKind kind = DataTransferItem::KindFromData(aData);
+    if (kind == DataTransferItem::KIND_OTHER) {
+      NS_WARNING("Disallowing adding non string/file types to DataTransfer");
+      return false;
+    }
+
+    if (aType.EqualsASCII(kFileMime) ||
+        aType.EqualsASCII(kFilePromiseMime)) {
+      NS_WARNING("Disallowing adding x-moz-file or x-moz-file-promize types to DataTransfer");
+      return false;
+    }
+  }
+  return true;
+}
+
+void
+DataTransfer::TypesListMayHaveChanged()
+{
+  DataTransferBinding::ClearCachedTypesValue(this);
+}
+
+nsresult
+DataTransfer::SetDataAtInternal(const nsAString& aFormat, nsIVariant* aData,
+                                uint32_t aIndex,
+                                nsIPrincipal* aSubjectPrincipal)
+{
+  if (aFormat.IsEmpty()) {
+    return NS_OK;
+  }
+
+  if (mReadOnly) {
+    return NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR;
+  }
+
+  // Specifying an index less than the current length will replace an existing
+  // item. Specifying an index equal to the current length will add a new item.
+  if (aIndex > MozItemCount()) {
+    return NS_ERROR_DOM_INDEX_SIZE_ERR;
+  }
+
+  // Only the first item is valid for clipboard events
+  if (aIndex > 0 &&
+      (mEventMessage == eCut || mEventMessage == eCopy ||
+       mEventMessage == ePaste)) {
+    return NS_ERROR_DOM_INDEX_SIZE_ERR;
+  }
+
+  // Don't allow the custom type to be assigned.
+  if (aFormat.EqualsLiteral(kCustomTypesMime)) {
+    return NS_ERROR_TYPE_ERR;
+  }
+
+  if (!PrincipalMaySetData(aFormat, aData, aSubjectPrincipal)) {
+    return NS_ERROR_DOM_SECURITY_ERR;
+  }
+
+  return SetDataWithPrincipal(aFormat, aData, aIndex, aSubjectPrincipal);
+}
+
+void
+DataTransfer::MozSetDataAt(JSContext* aCx, const nsAString& aFormat,
+                           JS::Handle<JS::Value> aData, uint32_t aIndex,
+                           nsIPrincipal& aSubjectPrincipal,
+                           ErrorResult& aRv)
+{
+  nsCOMPtr<nsIVariant> data;
+  aRv = nsContentUtils::XPConnect()->JSValToVariant(aCx, aData,
+                                                    getter_AddRefs(data));
+  if (!aRv.Failed()) {
+    aRv = SetDataAtInternal(aFormat, data, aIndex, &aSubjectPrincipal);
+  }
+}
+
+void
+DataTransfer::MozClearDataAt(const nsAString& aFormat, uint32_t aIndex,
+                             nsIPrincipal& aSubjectPrincipal,
+                             ErrorResult& aRv)
+{
+  if (mReadOnly) {
+    aRv.Throw(NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR);
+    return;
+  }
+
+  if (aIndex >= MozItemCount()) {
+    aRv.Throw(NS_ERROR_DOM_INDEX_SIZE_ERR);
+    return;
+  }
+
+  // Only the first item is valid for clipboard events
+  if (aIndex > 0 &&
+      (mEventMessage == eCut || mEventMessage == eCopy ||
+       mEventMessage == ePaste)) {
+    aRv.Throw(NS_ERROR_DOM_INDEX_SIZE_ERR);
+    return;
+  }
+
+  MozClearDataAtHelper(aFormat, aIndex, aSubjectPrincipal, aRv);
+
+  // If we just cleared the 0-th index, and there are still more than 1 indexes
+  // remaining, MozClearDataAt should cause the 1st index to become the 0th
+  // index. This should _only_ happen when the MozClearDataAt function is
+  // explicitly called by script, as this behavior is inconsistent with spec.
+  // (however, so is the MozClearDataAt API)
+
+  if (aIndex == 0 && mItems->MozItemCount() > 1 &&
+      mItems->MozItemsAt(0)->Length() == 0) {
+    mItems->PopIndexZero();
+  }
+}
+
+void
+DataTransfer::MozClearDataAtHelper(const nsAString& aFormat, uint32_t aIndex,
+                                   nsIPrincipal& aSubjectPrincipal,
+                                   ErrorResult& aRv)
+{
+  MOZ_ASSERT(!mReadOnly);
+  MOZ_ASSERT(aIndex < MozItemCount());
+  MOZ_ASSERT(aIndex == 0 ||
+             (mEventMessage != eCut && mEventMessage != eCopy &&
+              mEventMessage != ePaste));
+
+  nsAutoString format;
+  GetRealFormat(aFormat, format);
+
+  mItems->MozRemoveByTypeAt(format, aIndex, aSubjectPrincipal, aRv);
+}
+
+void
+DataTransfer::SetDragImage(Element& aImage, int32_t aX, int32_t aY,
+                           ErrorResult& aRv)
+{
+  if (mReadOnly) {
+    aRv.Throw(NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR);
+    return;
+  }
+
+  mDragImage = &aImage;
+  mDragImageX = aX;
+  mDragImageY = aY;
+}
+
+NS_IMETHODIMP
+DataTransfer::SetDragImage(nsIDOMElement* aImage, int32_t aX, int32_t aY)
+{
+  ErrorResult rv;
+  nsCOMPtr<Element> image = do_QueryInterface(aImage);
+  if (image) {
+    SetDragImage(*image, aX, aY, rv);
+  }
+  return rv.StealNSResult();
+}
+
+already_AddRefed<Promise>
+DataTransfer::GetFilesAndDirectories(nsIPrincipal& aSubjectPrincipal,
+                                     ErrorResult& aRv)
+{
+  nsCOMPtr<nsINode> parentNode = do_QueryInterface(mParent);
+  if (!parentNode) {
+    aRv.Throw(NS_ERROR_FAILURE);
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIGlobalObject> global = parentNode->OwnerDoc()->GetScopeObject();
+  MOZ_ASSERT(global);
+  if (!global) {
+    aRv.Throw(NS_ERROR_FAILURE);
+    return nullptr;
+  }
+
+  RefPtr<Promise> p = Promise::Create(global, aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  RefPtr<FileList> files = mItems->Files(&aSubjectPrincipal);
+  if (NS_WARN_IF(!files)) {
+    return nullptr;
+  }
+
+  Sequence<RefPtr<File>> filesSeq;
+  files->ToSequence(filesSeq, aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  p->MaybeResolve(filesSeq);
+
+  return p.forget();
+}
+
+already_AddRefed<Promise>
+DataTransfer::GetFiles(bool aRecursiveFlag,
+                       nsIPrincipal& aSubjectPrincipal,
+                       ErrorResult& aRv)
+{
+  // Currently we don't support directories.
+  return GetFilesAndDirectories(aSubjectPrincipal, aRv);
+}
+
+void
+DataTransfer::AddElement(Element& aElement, ErrorResult& aRv)
+{
+  if (mReadOnly) {
+    aRv.Throw(NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR);
+    return;
+  }
+
+  mDragTarget = &aElement;
+}
+
+NS_IMETHODIMP
+DataTransfer::AddElement(nsIDOMElement* aElement)
+{
+  NS_ENSURE_TRUE(aElement, NS_ERROR_NULL_POINTER);
+
+  nsCOMPtr<Element> element = do_QueryInterface(aElement);
+  NS_ENSURE_TRUE(element, NS_ERROR_INVALID_ARG);
+
+  ErrorResult rv;
+  AddElement(*element, rv);
+  return rv.StealNSResult();
+}
+
+nsresult
+DataTransfer::Clone(nsISupports* aParent, EventMessage aEventMessage,
+                    bool aUserCancelled, bool aIsCrossDomainSubFrameDrop,
+                    DataTransfer** aNewDataTransfer)
+{
+  RefPtr<DataTransfer> newDataTransfer =
+    new DataTransfer(aParent, aEventMessage, mEffectAllowed, mCursorState,
+                     mIsExternal, aUserCancelled, aIsCrossDomainSubFrameDrop,
+                     mClipboardType, mItems, mDragImage, mDragImageX,
+                     mDragImageY);
+
+  newDataTransfer.forget(aNewDataTransfer);
+  return NS_OK;
+}
+
+already_AddRefed<nsIArray>
+DataTransfer::GetTransferables(nsIDOMNode* aDragTarget)
+{
+  MOZ_ASSERT(aDragTarget);
+
+  nsCOMPtr<nsINode> dragNode = do_QueryInterface(aDragTarget);
+  if (!dragNode) {
+    return nullptr;
+  }
+
+  nsIDocument* doc = dragNode->GetComposedDoc();
+  if (!doc) {
+    return nullptr;
+  }
+
+  return GetTransferables(doc->GetLoadContext());
+}
+
+already_AddRefed<nsIArray>
+DataTransfer::GetTransferables(nsILoadContext* aLoadContext)
+{
+  nsCOMPtr<nsIMutableArray> transArray = nsArray::Create();
+  if (!transArray) {
+    return nullptr;
+  }
+
+  uint32_t count = MozItemCount();
+  for (uint32_t i = 0; i < count; i++) {
+    nsCOMPtr<nsITransferable> transferable = GetTransferable(i, aLoadContext);
+    if (transferable) {
+      transArray->AppendElement(transferable, /*weak =*/ false);
+    }
+  }
+
+  return transArray.forget();
+}
+
+already_AddRefed<nsITransferable>
+DataTransfer::GetTransferable(uint32_t aIndex, nsILoadContext* aLoadContext)
+{
+  if (aIndex >= MozItemCount()) {
+    return nullptr;
+  }
+
+  const nsTArray<RefPtr<DataTransferItem>>& item = *mItems->MozItemsAt(aIndex);
+  uint32_t count = item.Length();
+  if (!count) {
+    return nullptr;
+  }
+
+  nsCOMPtr<nsITransferable> transferable =
+    do_CreateInstance("@mozilla.org/widget/transferable;1");
+  if (!transferable) {
+    return nullptr;
+  }
+  transferable->Init(aLoadContext);
+
+  nsCOMPtr<nsIStorageStream> storageStream;
+  nsCOMPtr<nsIBinaryOutputStream> stream;
+
+  bool added = false;
+  bool handlingCustomFormats = true;
+
+  // When writing the custom data, we need to ensure that there is sufficient
+  // space for a (uint32_t) data ending type, and the null byte character at
+  // the end of the nsCString. We claim that space upfront and store it in
+  // baseLength. This value will be set to zero if a write error occurs
+  // indicating that the data and length are no longer valid.
+  const uint32_t baseLength = sizeof(uint32_t) + 1;
+  uint32_t totalCustomLength = baseLength;
+
+  const char* knownFormats[] = {
+    kTextMime, kHTMLMime, kNativeHTMLMime, kRTFMime,
+    kURLMime, kURLDataMime, kURLDescriptionMime, kURLPrivateMime,
+    kPNGImageMime, kJPEGImageMime, kGIFImageMime, kNativeImageMime,
+    kFileMime, kFilePromiseMime, kFilePromiseURLMime,
+    kFilePromiseDestFilename, kFilePromiseDirectoryMime,
+    kMozTextInternal, kHTMLContext, kHTMLInfo };
+
+  /*
+   * Two passes are made here to iterate over all of the types. First, look for
+   * any types that are not in the list of known types. For this pass,
+   * handlingCustomFormats will be true. Data that corresponds to unknown types
+   * will be pulled out and inserted into a single type (kCustomTypesMime) by
+   * writing the data into a stream.
+   *
+   * The second pass will iterate over the formats looking for known types.
+   * These are added as is. The unknown types are all then inserted as a single
+   * type (kCustomTypesMime) in the same position of the first custom type. This
+   * model is used to maintain the format order as best as possible.
+   *
+   * The format of the kCustomTypesMime type is one or more of the following
+   * stored sequentially:
+   *   <32-bit> type (only none or string is supported)
+   *   <32-bit> length of format
+   *   <wide string> format
+   *   <32-bit> length of data
+   *   <wide string> data
+   * A type of eCustomClipboardTypeId_None ends the list, without any following
+   * data.
+   */
+  do {
+    for (uint32_t f = 0; f < count; f++) {
+      RefPtr<DataTransferItem> formatitem = item[f];
+      nsCOMPtr<nsIVariant> variant = formatitem->DataNoSecurityCheck();
+      if (!variant) { // skip empty items
+        continue;
+      }
+
+      nsAutoString type;
+      formatitem->GetInternalType(type);
+
+      // If the data is of one of the well-known formats, use it directly.
+      bool isCustomFormat = true;
+      for (uint32_t f = 0; f < ArrayLength(knownFormats); f++) {
+        if (type.EqualsASCII(knownFormats[f])) {
+          isCustomFormat = false;
+          break;
+        }
+      }
+
+      uint32_t lengthInBytes;
+      nsCOMPtr<nsISupports> convertedData;
+
+      if (handlingCustomFormats) {
+        if (!ConvertFromVariant(variant, getter_AddRefs(convertedData),
+                                &lengthInBytes)) {
+          continue;
+        }
+
+        // When handling custom types, add the data to the stream if this is a
+        // custom type. If totalCustomLength is 0, then a write error occurred
+        // on a previous item, so ignore any others.
+        if (isCustomFormat && totalCustomLength > 0) {
+          // If it isn't a string, just ignore it. The dataTransfer is cached in
+          // the drag sesion during drag-and-drop, so non-strings will be
+          // available when dragging locally.
+          nsCOMPtr<nsISupportsString> str(do_QueryInterface(convertedData));
+          if (str) {
+            nsAutoString data;
+            str->GetData(data);
+
+            if (!stream) {
+              // Create a storage stream to write to.
+              NS_NewStorageStream(1024, UINT32_MAX, getter_AddRefs(storageStream));
+
+              nsCOMPtr<nsIOutputStream> outputStream;
+              storageStream->GetOutputStream(0, getter_AddRefs(outputStream));
+
+              stream = do_CreateInstance("@mozilla.org/binaryoutputstream;1");
+              stream->SetOutputStream(outputStream);
+            }
+
+            CheckedInt<uint32_t> formatLength =
+              CheckedInt<uint32_t>(type.Length()) * sizeof(nsString::char_type);
+
+            // The total size of the stream is the format length, the data
+            // length, two integers to hold the lengths and one integer for
+            // the string flag. Guard against large data by ignoring any that
+            // don't fit.
+            CheckedInt<uint32_t> newSize = formatLength + totalCustomLength +
+                                           lengthInBytes + (sizeof(uint32_t) * 3);
+            if (newSize.isValid()) {
+              // If a write error occurs, set totalCustomLength to 0 so that
+              // further processing gets ignored.
+              nsresult rv = stream->Write32(eCustomClipboardTypeId_String);
+              if (NS_WARN_IF(NS_FAILED(rv))) {
+                totalCustomLength = 0;
+                continue;
+              }
+              rv = stream->Write32(formatLength.value());
+              if (NS_WARN_IF(NS_FAILED(rv))) {
+                totalCustomLength = 0;
+                continue;
+              }
+              rv = stream->WriteBytes((const char *)type.get(), formatLength.value());
+              if (NS_WARN_IF(NS_FAILED(rv))) {
+                totalCustomLength = 0;
+                continue;
+              }
+              rv = stream->Write32(lengthInBytes);
+              if (NS_WARN_IF(NS_FAILED(rv))) {
+                totalCustomLength = 0;
+                continue;
+              }
+              rv = stream->WriteBytes((const char *)data.get(), lengthInBytes);
+              if (NS_WARN_IF(NS_FAILED(rv))) {
+                totalCustomLength = 0;
+                continue;
+              }
+
+              totalCustomLength = newSize.value();
+            }
+          }
+        }
+      } else if (isCustomFormat && stream) {
+        // This is the second pass of the loop (handlingCustomFormats is false).
+        // When encountering the first custom format, append all of the stream
+        // at this position. If totalCustomLength is 0 indicating a write error
+        // occurred, or no data has been added to it, don't output anything,
+        if (totalCustomLength > baseLength) {
+          // Write out an end of data terminator.
+          nsresult rv = stream->Write32(eCustomClipboardTypeId_None);
+          if (NS_SUCCEEDED(rv)) {
+            nsCOMPtr<nsIInputStream> inputStream;
+            storageStream->NewInputStream(0, getter_AddRefs(inputStream));
+
+            RefPtr<nsStringBuffer> stringBuffer =
+              nsStringBuffer::Alloc(totalCustomLength);
+
+            // Subtract off the null terminator when reading.
+            totalCustomLength--;
+
+            // Read the data from the stream and add a null-terminator as
+            // ToString needs it.
+            uint32_t amountRead;
+            rv = inputStream->Read(static_cast<char*>(stringBuffer->Data()),
+                              totalCustomLength, &amountRead);
+            if (NS_SUCCEEDED(rv)) {
+              static_cast<char*>(stringBuffer->Data())[amountRead] = 0;
+
+              nsCString str;
+              stringBuffer->ToString(totalCustomLength, str);
+              nsCOMPtr<nsISupportsCString>
+                strSupports(do_CreateInstance(NS_SUPPORTS_CSTRING_CONTRACTID));
+              strSupports->SetData(str);
+
+              nsresult rv = transferable->SetTransferData(kCustomTypesMime,
+                                                          strSupports,
+                                                          totalCustomLength);
+              if (NS_FAILED(rv)) {
+                return nullptr;
+              }
+
+              added = true;
+            }
+          }
+        }
+
+        // Clear the stream so it doesn't get used again.
+        stream = nullptr;
+      } else {
+        // This is the second pass of the loop and a known type is encountered.
+        // Add it as is.
+        if (!ConvertFromVariant(variant, getter_AddRefs(convertedData),
+                                &lengthInBytes)) {
+          continue;
+        }
+
+        // The underlying drag code uses text/unicode, so use that instead of
+        // text/plain
+        const char* format;
+        NS_ConvertUTF16toUTF8 utf8format(type);
+        if (utf8format.EqualsLiteral(kTextMime)) {
+          format = kUnicodeMime;
+        } else {
+          format = utf8format.get();
+        }
+
+        // If a converter is set for a format, set the converter for the
+        // transferable and don't add the item
+        nsCOMPtr<nsIFormatConverter> converter =
+          do_QueryInterface(convertedData);
+        if (converter) {
+          transferable->AddDataFlavor(format);
+          transferable->SetConverter(converter);
+          continue;
+        }
+
+        nsresult rv = transferable->SetTransferData(format, convertedData,
+                                                    lengthInBytes);
+        if (NS_FAILED(rv)) {
+          return nullptr;
+        }
+
+        added = true;
+      }
+    }
+
+    handlingCustomFormats = !handlingCustomFormats;
+  } while (!handlingCustomFormats);
+
+  // only return the transferable if data was successfully added to it
+  if (added) {
+    return transferable.forget();
+  }
+
+  return nullptr;
+}
+
+bool
+DataTransfer::ConvertFromVariant(nsIVariant* aVariant,
+                                 nsISupports** aSupports,
+                                 uint32_t* aLength) const
+{
+  *aSupports = nullptr;
+  *aLength = 0;
+
+  uint16_t type;
+  aVariant->GetDataType(&type);
+  if (type == nsIDataType::VTYPE_INTERFACE ||
+      type == nsIDataType::VTYPE_INTERFACE_IS) {
+    nsCOMPtr<nsISupports> data;
+    if (NS_FAILED(aVariant->GetAsISupports(getter_AddRefs(data)))) {
+      return false;
+    }
+
+    nsCOMPtr<nsIFlavorDataProvider> fdp = do_QueryInterface(data);
+    if (fdp) {
+      // for flavour data providers, use kFlavorHasDataProvider (which has the
+      // value 0) as the length.
+      fdp.forget(aSupports);
+      *aLength = nsITransferable::kFlavorHasDataProvider;
+    }
+    else {
+      // wrap the item in an nsISupportsInterfacePointer
+      nsCOMPtr<nsISupportsInterfacePointer> ptrSupports =
+        do_CreateInstance(NS_SUPPORTS_INTERFACE_POINTER_CONTRACTID);
+      if (!ptrSupports) {
+        return false;
+      }
+
+      ptrSupports->SetData(data);
+      ptrSupports.forget(aSupports);
+
+      *aLength = sizeof(nsISupportsInterfacePointer *);
+    }
+
+    return true;
+  }
+
+  char16_t* chrs;
+  uint32_t len = 0;
+  nsresult rv = aVariant->GetAsWStringWithSize(&len, &chrs);
+  if (NS_FAILED(rv)) {
+    return false;
+  }
+
+  nsAutoString str;
+  str.Adopt(chrs, len);
+
+  nsCOMPtr<nsISupportsString>
+    strSupports(do_CreateInstance(NS_SUPPORTS_STRING_CONTRACTID));
+  if (!strSupports) {
+    return false;
+  }
+
+  strSupports->SetData(str);
+
+  strSupports.forget(aSupports);
+
+  // each character is two bytes
+  *aLength = str.Length() << 1;
+
+  return true;
+}
+
+void
+DataTransfer::ClearAll()
+{
+  mItems->ClearAllItems();
+}
+
+uint32_t
+DataTransfer::MozItemCount() const
+{
+  return mItems->MozItemCount();
+}
+
+nsresult
+DataTransfer::SetDataWithPrincipal(const nsAString& aFormat,
+                                   nsIVariant* aData,
+                                   uint32_t aIndex,
+                                   nsIPrincipal* aPrincipal)
+{
+  nsAutoString format;
+  GetRealFormat(aFormat, format);
+
+  ErrorResult rv;
+  RefPtr<DataTransferItem> item =
+    mItems->SetDataWithPrincipal(format, aData, aIndex, aPrincipal,
+                                 /* aInsertOnly = */ false,
+                                 /* aHidden= */ false,
+                                 rv);
+  return rv.StealNSResult();
+}
+
+void
+DataTransfer::SetDataWithPrincipalFromOtherProcess(const nsAString& aFormat,
+                                                   nsIVariant* aData,
+                                                   uint32_t aIndex,
+                                                   nsIPrincipal* aPrincipal,
+                                                   bool aHidden)
+{
+  if (aFormat.EqualsLiteral(kCustomTypesMime)) {
+    FillInExternalCustomTypes(aData, aIndex, aPrincipal);
+  } else {
+    nsAutoString format;
+    GetRealFormat(aFormat, format);
+
+    ErrorResult rv;
+    RefPtr<DataTransferItem> item =
+      mItems->SetDataWithPrincipal(format, aData, aIndex, aPrincipal,
+                                   /* aInsertOnly = */ false, aHidden, rv);
+    if (NS_WARN_IF(rv.Failed())) {
+      rv.SuppressException();
+    }
+  }
+}
+
+void
+DataTransfer::GetRealFormat(const nsAString& aInFormat,
+                            nsAString& aOutFormat) const
+{
+  // treat text/unicode as equivalent to text/plain
+  nsAutoString lowercaseFormat;
+  nsContentUtils::ASCIIToLower(aInFormat, lowercaseFormat);
+  if (lowercaseFormat.EqualsLiteral("text") ||
+      lowercaseFormat.EqualsLiteral("text/unicode")) {
+    aOutFormat.AssignLiteral("text/plain");
+    return;
+  }
+
+  if (lowercaseFormat.EqualsLiteral("url")) {
+    aOutFormat.AssignLiteral("text/uri-list");
+    return;
+  }
+
+  aOutFormat.Assign(lowercaseFormat);
+}
+
+nsresult
+DataTransfer::CacheExternalData(const char* aFormat, uint32_t aIndex,
+                                nsIPrincipal* aPrincipal, bool aHidden)
+{
+  ErrorResult rv;
+  RefPtr<DataTransferItem> item;
+
+  if (strcmp(aFormat, kUnicodeMime) == 0) {
+    item = mItems->SetDataWithPrincipal(NS_LITERAL_STRING("text/plain"), nullptr,
+                                        aIndex, aPrincipal, false, aHidden, rv);
+    if (NS_WARN_IF(rv.Failed())) {
+      return rv.StealNSResult();
+    }
+    return NS_OK;
+  }
+
+  if (strcmp(aFormat, kURLDataMime) == 0) {
+    item = mItems->SetDataWithPrincipal(NS_LITERAL_STRING("text/uri-list"), nullptr,
+                                        aIndex, aPrincipal, false, aHidden, rv);
+    if (NS_WARN_IF(rv.Failed())) {
+      return rv.StealNSResult();
+    }
+    return NS_OK;
+  }
+
+  nsAutoString format;
+  GetRealFormat(NS_ConvertUTF8toUTF16(aFormat), format);
+  item = mItems->SetDataWithPrincipal(format, nullptr, aIndex,
+                                      aPrincipal, false, aHidden, rv);
+  if (NS_WARN_IF(rv.Failed())) {
+    return rv.StealNSResult();
+  }
+  return NS_OK;
+}
+
+void
+DataTransfer::CacheExternalDragFormats()
+{
+  // Called during the constructor to cache the formats available from an
+  // external drag. The data associated with each format will be set to null.
+  // This data will instead only be retrieved in FillInExternalDragData when
+  // asked for, as it may be time consuming for the source application to
+  // generate it.
+
+  nsCOMPtr<nsIDragSession> dragSession = nsContentUtils::GetDragSession();
+  if (!dragSession) {
+    return;
+  }
+
+  // make sure that the system principal is used for external drags
+  nsIScriptSecurityManager* ssm = nsContentUtils::GetSecurityManager();
+  nsCOMPtr<nsIPrincipal> sysPrincipal;
+  ssm->GetSystemPrincipal(getter_AddRefs(sysPrincipal));
+
+  // there isn't a way to get a list of the formats that might be available on
+  // all platforms, so just check for the types that can actually be imported
+  // XXXndeakin there are some other formats but those are platform specific.
+  // NOTE: kFileMime must have index 0
+  const char* formats[] = { kFileMime, kHTMLMime, kURLMime, kURLDataMime,
+                            kUnicodeMime, kPNGImageMime };
+
+  uint32_t count;
+  dragSession->GetNumDropItems(&count);
+  for (uint32_t c = 0; c < count; c++) {
+    bool hasFileData = false;
+    dragSession->IsDataFlavorSupported(kFileMime, &hasFileData);
+
+    // First, check for the special format that holds custom types.
+    bool supported;
+    dragSession->IsDataFlavorSupported(kCustomTypesMime, &supported);
+    if (supported) {
+      FillInExternalCustomTypes(c, sysPrincipal);
+    }
+
+    for (uint32_t f = 0; f < ArrayLength(formats); f++) {
+      // IsDataFlavorSupported doesn't take an index as an argument and just
+      // checks if any of the items support a particular flavor, even though
+      // the GetData method does take an index. Here, we just assume that
+      // every item being dragged has the same set of flavors.
+      bool supported;
+      dragSession->IsDataFlavorSupported(formats[f], &supported);
+      // if the format is supported, add an item to the array with null as
+      // the data. When retrieved, GetRealData will read the data.
+      if (supported) {
+        CacheExternalData(formats[f], c, sysPrincipal, /* hidden = */ f && hasFileData);
+      }
+    }
+  }
+}
+
+void
+DataTransfer::CacheExternalClipboardFormats()
+{
+  NS_ASSERTION(mEventMessage == ePaste,
+               "caching clipboard data for invalid event");
+
+  // Called during the constructor for paste events to cache the formats
+  // available on the clipboard. As with CacheExternalDragFormats, the
+  // data will only be retrieved when needed.
+
+  nsCOMPtr<nsIClipboard> clipboard =
+    do_GetService("@mozilla.org/widget/clipboard;1");
+  if (!clipboard || mClipboardType < 0) {
+    return;
+  }
+
+  nsIScriptSecurityManager* ssm = nsContentUtils::GetSecurityManager();
+  nsCOMPtr<nsIPrincipal> sysPrincipal;
+  ssm->GetSystemPrincipal(getter_AddRefs(sysPrincipal));
+
+  // Check if the clipboard has any files
+  bool hasFileData = false;
+  const char *fileMime[] = { kFileMime };
+  clipboard->HasDataMatchingFlavors(fileMime, 1, mClipboardType, &hasFileData);
+
+  // We will be ignoring any application/x-moz-file files found in the paste
+  // datatransfer within e10s, as they will fail to be sent over IPC. Because of
+  // that, we will unset hasFileData, whether or not it would have been set.
+  // (bug 1308007)
+  if (XRE_IsContentProcess()) {
+    hasFileData = false;
+  }
+
+  // there isn't a way to get a list of the formats that might be available on
+  // all platforms, so just check for the types that can actually be imported.
+  // NOTE: kCustomTypesMime must have index 0, kFileMime index 1
+  const char* formats[] = { kCustomTypesMime, kFileMime, kHTMLMime, kRTFMime,
+                            kURLMime, kURLDataMime, kUnicodeMime, kPNGImageMime };
+
+  for (uint32_t f = 0; f < mozilla::ArrayLength(formats); ++f) {
+    // check each format one at a time
+    bool supported;
+    clipboard->HasDataMatchingFlavors(&(formats[f]), 1, mClipboardType,
+                                      &supported);
+    // if the format is supported, add an item to the array with null as
+    // the data. When retrieved, GetRealData will read the data.
+    if (supported) {
+      if (f == 0) {
+        FillInExternalCustomTypes(0, sysPrincipal);
+      } else {
+        // In non-e10s we support pasting files from explorer.exe.
+        // Unfortunately, we fail to send that data over IPC in e10s, so we
+        // don't want to add the item to the DataTransfer and end up producing a
+        // null `application/x-moz-file`. (bug 1308007)
+        if (XRE_IsContentProcess() && f == 1) {
+          continue;
+        }
+
+        // If we aren't the file data, and we have file data, we want to be hidden
+        CacheExternalData(formats[f], 0, sysPrincipal, /* hidden = */ f != 1 && hasFileData);
+      }
+    }
+  }
+}
+
+void
+DataTransfer::FillAllExternalData()
+{
+  if (mIsExternal) {
+    for (uint32_t i = 0; i < MozItemCount(); ++i) {
+      const nsTArray<RefPtr<DataTransferItem>>& items = *mItems->MozItemsAt(i);
+      for (uint32_t j = 0; j < items.Length(); ++j) {
+        MOZ_ASSERT(items[j]->Index() == i);
+
+        items[j]->FillInExternalData();
+      }
+    }
+  }
+}
+
+void
+DataTransfer::FillInExternalCustomTypes(uint32_t aIndex,
+                                        nsIPrincipal* aPrincipal)
+{
+  RefPtr<DataTransferItem> item = new DataTransferItem(this,
+                                                       NS_LITERAL_STRING(kCustomTypesMime),
+                                                       DataTransferItem::KIND_STRING);
+  item->SetIndex(aIndex);
+
+  nsCOMPtr<nsIVariant> variant = item->DataNoSecurityCheck();
+  if (!variant) {
+    return;
+  }
+
+  FillInExternalCustomTypes(variant, aIndex, aPrincipal);
+}
+
+void
+DataTransfer::FillInExternalCustomTypes(nsIVariant* aData, uint32_t aIndex,
+                                        nsIPrincipal* aPrincipal)
+{
+  char* chrs;
+  uint32_t len = 0;
+  nsresult rv = aData->GetAsStringWithSize(&len, &chrs);
+  if (NS_FAILED(rv)) {
+    return;
+  }
+
+  nsAutoCString str;
+  str.Adopt(chrs, len);
+
+  nsCOMPtr<nsIInputStream> stringStream;
+  NS_NewCStringInputStream(getter_AddRefs(stringStream), str);
+
+  nsCOMPtr<nsIBinaryInputStream> stream =
+    do_CreateInstance("@mozilla.org/binaryinputstream;1");
+  if (!stream) {
+    return;
+  }
+
+  rv = stream->SetInputStream(stringStream);
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  uint32_t type;
+  do {
+    rv = stream->Read32(&type);
+    NS_ENSURE_SUCCESS_VOID(rv);
+    if (type == eCustomClipboardTypeId_String) {
+      uint32_t formatLength;
+      rv = stream->Read32(&formatLength);
+      NS_ENSURE_SUCCESS_VOID(rv);
+      char* formatBytes;
+      rv = stream->ReadBytes(formatLength, &formatBytes);
+      NS_ENSURE_SUCCESS_VOID(rv);
+      nsAutoString format;
+      format.Adopt(reinterpret_cast<char16_t*>(formatBytes),
+                   formatLength / sizeof(char16_t));
+
+      uint32_t dataLength;
+      rv = stream->Read32(&dataLength);
+      NS_ENSURE_SUCCESS_VOID(rv);
+      char* dataBytes;
+      rv = stream->ReadBytes(dataLength, &dataBytes);
+      NS_ENSURE_SUCCESS_VOID(rv);
+      nsAutoString data;
+      data.Adopt(reinterpret_cast<char16_t*>(dataBytes),
+                 dataLength / sizeof(char16_t));
+
+      RefPtr<nsVariantCC> variant = new nsVariantCC();
+      rv = variant->SetAsAString(data);
+      NS_ENSURE_SUCCESS_VOID(rv);
+
+      SetDataWithPrincipal(format, variant, aIndex, aPrincipal);
+    }
+  } while (type != eCustomClipboardTypeId_None);
+}
+
+} // namespace dom
+} // namespace mozilla