Add m-esr52 at 52.6.0

1 files changed, 5244 insertions, 0 deletions

diff --git a/editor/libeditor/EditorBase.cpp b/editor/libeditor/EditorBase.cpp
new file mode 100644
index 000000000..13505b2d3
--- /dev/null
+++ b/editor/libeditor/EditorBase.cpp
@@ -0,0 +1,5244 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/EditorBase.h"
+
+#include "mozilla/DebugOnly.h"          // for DebugOnly
+
+#include <stdio.h>                      // for nullptr, stdout
+#include <string.h>                     // for strcmp
+
+#include "ChangeAttributeTransaction.h" // for ChangeAttributeTransaction
+#include "CompositionTransaction.h"     // for CompositionTransaction
+#include "CreateElementTransaction.h"   // for CreateElementTransaction
+#include "DeleteNodeTransaction.h"      // for DeleteNodeTransaction
+#include "DeleteRangeTransaction.h"     // for DeleteRangeTransaction
+#include "DeleteTextTransaction.h"      // for DeleteTextTransaction
+#include "EditAggregateTransaction.h"   // for EditAggregateTransaction
+#include "EditorEventListener.h"        // for EditorEventListener
+#include "InsertNodeTransaction.h"      // for InsertNodeTransaction
+#include "InsertTextTransaction.h"      // for InsertTextTransaction
+#include "JoinNodeTransaction.h"        // for JoinNodeTransaction
+#include "PlaceholderTransaction.h"     // for PlaceholderTransaction
+#include "SplitNodeTransaction.h"       // for SplitNodeTransaction
+#include "StyleSheetTransactions.h"     // for AddStyleSheetTransaction, etc.
+#include "TextEditUtils.h"              // for TextEditUtils
+#include "mozFlushType.h"               // for mozFlushType::Flush_Frames
+#include "mozInlineSpellChecker.h"      // for mozInlineSpellChecker
+#include "mozilla/CheckedInt.h"         // for CheckedInt
+#include "mozilla/EditorUtils.h"        // for AutoRules, etc.
+#include "mozilla/EditTransactionBase.h" // for EditTransactionBase
+#include "mozilla/IMEStateManager.h"    // for IMEStateManager
+#include "mozilla/Preferences.h"        // for Preferences
+#include "mozilla/dom/Selection.h"      // for Selection, etc.
+#include "mozilla/Services.h"           // for GetObserverService
+#include "mozilla/TextComposition.h"    // for TextComposition
+#include "mozilla/TextEvents.h"
+#include "mozilla/dom/Element.h"        // for Element, nsINode::AsElement
+#include "mozilla/dom/Text.h"
+#include "mozilla/dom/Event.h"
+#include "mozilla/mozalloc.h"           // for operator new, etc.
+#include "nsAString.h"                  // for nsAString_internal::Length, etc.
+#include "nsCCUncollectableMarker.h"    // for nsCCUncollectableMarker
+#include "nsCaret.h"                    // for nsCaret
+#include "nsCaseTreatment.h"
+#include "nsCharTraits.h"               // for NS_IS_HIGH_SURROGATE, etc.
+#include "nsComponentManagerUtils.h"    // for do_CreateInstance
+#include "nsComputedDOMStyle.h"         // for nsComputedDOMStyle
+#include "nsContentUtils.h"             // for nsContentUtils
+#include "nsDOMString.h"                // for DOMStringIsNull
+#include "nsDebug.h"                    // for NS_ENSURE_TRUE, etc.
+#include "nsError.h"                    // for NS_OK, etc.
+#include "nsFocusManager.h"             // for nsFocusManager
+#include "nsFrameSelection.h"           // for nsFrameSelection
+#include "nsGkAtoms.h"                  // for nsGkAtoms, nsGkAtoms::dir
+#include "nsIAbsorbingTransaction.h"    // for nsIAbsorbingTransaction
+#include "nsIAtom.h"                    // for nsIAtom
+#include "nsIContent.h"                 // for nsIContent
+#include "nsIDOMAttr.h"                 // for nsIDOMAttr
+#include "nsIDOMCharacterData.h"        // for nsIDOMCharacterData
+#include "nsIDOMDocument.h"             // for nsIDOMDocument
+#include "nsIDOMElement.h"              // for nsIDOMElement
+#include "nsIDOMEvent.h"                // for nsIDOMEvent
+#include "nsIDOMEventListener.h"        // for nsIDOMEventListener
+#include "nsIDOMEventTarget.h"          // for nsIDOMEventTarget
+#include "nsIDOMHTMLElement.h"          // for nsIDOMHTMLElement
+#include "nsIDOMKeyEvent.h"             // for nsIDOMKeyEvent, etc.
+#include "nsIDOMMozNamedAttrMap.h"      // for nsIDOMMozNamedAttrMap
+#include "nsIDOMMouseEvent.h"           // for nsIDOMMouseEvent
+#include "nsIDOMNode.h"                 // for nsIDOMNode, etc.
+#include "nsIDOMNodeList.h"             // for nsIDOMNodeList
+#include "nsIDOMText.h"                 // for nsIDOMText
+#include "nsIDocument.h"                // for nsIDocument
+#include "nsIDocumentStateListener.h"   // for nsIDocumentStateListener
+#include "nsIEditActionListener.h"      // for nsIEditActionListener
+#include "nsIEditorObserver.h"          // for nsIEditorObserver
+#include "nsIEditorSpellCheck.h"        // for nsIEditorSpellCheck
+#include "nsIFrame.h"                   // for nsIFrame
+#include "nsIHTMLDocument.h"            // for nsIHTMLDocument
+#include "nsIInlineSpellChecker.h"      // for nsIInlineSpellChecker, etc.
+#include "nsNameSpaceManager.h"        // for kNameSpaceID_None, etc.
+#include "nsINode.h"                    // for nsINode, etc.
+#include "nsIPlaintextEditor.h"         // for nsIPlaintextEditor, etc.
+#include "nsIPresShell.h"               // for nsIPresShell
+#include "nsISelectionController.h"     // for nsISelectionController, etc.
+#include "nsISelectionDisplay.h"        // for nsISelectionDisplay, etc.
+#include "nsISupportsBase.h"            // for nsISupports
+#include "nsISupportsUtils.h"           // for NS_ADDREF, NS_IF_ADDREF
+#include "nsITransaction.h"             // for nsITransaction
+#include "nsITransactionManager.h"
+#include "nsIWeakReference.h"           // for nsISupportsWeakReference
+#include "nsIWidget.h"                  // for nsIWidget, IMEState, etc.
+#include "nsPIDOMWindow.h"              // for nsPIDOMWindow
+#include "nsPresContext.h"              // for nsPresContext
+#include "nsRange.h"                    // for nsRange
+#include "nsReadableUtils.h"            // for EmptyString, ToNewCString
+#include "nsString.h"                   // for nsAutoString, nsString, etc.
+#include "nsStringFwd.h"                // for nsAFlatString
+#include "nsStyleConsts.h"              // for NS_STYLE_DIRECTION_RTL, etc.
+#include "nsStyleContext.h"             // for nsStyleContext
+#include "nsStyleStruct.h"              // for nsStyleDisplay, nsStyleText, etc.
+#include "nsStyleStructFwd.h"           // for nsIFrame::StyleUIReset, etc.
+#include "nsTextNode.h"                 // for nsTextNode
+#include "nsThreadUtils.h"              // for nsRunnable
+#include "nsTransactionManager.h"       // for nsTransactionManager
+#include "prtime.h"                     // for PR_Now
+
+class nsIOutputStream;
+class nsIParserService;
+class nsITransferable;
+
+#ifdef DEBUG
+#include "nsIDOMHTMLDocument.h"         // for nsIDOMHTMLDocument
+#endif
+
+// Defined in nsEditorRegistration.cpp
+extern nsIParserService *sParserService;
+
+namespace mozilla {
+
+using namespace dom;
+using namespace widget;
+
+/*****************************************************************************
+ * mozilla::EditorBase
+ *****************************************************************************/
+
+EditorBase::EditorBase()
+  : mPlaceHolderName(nullptr)
+  , mSelState(nullptr)
+  , mPhonetic(nullptr)
+  , mModCount(0)
+  , mFlags(0)
+  , mUpdateCount(0)
+  , mPlaceHolderBatch(0)
+  , mAction(EditAction::none)
+  , mIMETextOffset(0)
+  , mIMETextLength(0)
+  , mDirection(eNone)
+  , mDocDirtyState(-1)
+  , mSpellcheckCheckboxState(eTriUnset)
+  , mShouldTxnSetSelection(true)
+  , mDidPreDestroy(false)
+  , mDidPostCreate(false)
+  , mDispatchInputEvent(true)
+  , mIsInEditAction(false)
+  , mHidingCaret(false)
+{
+}
+
+EditorBase::~EditorBase()
+{
+  NS_ASSERTION(!mDocWeak || mDidPreDestroy, "Why PreDestroy hasn't been called?");
+
+  if (mComposition) {
+    mComposition->OnEditorDestroyed();
+    mComposition = nullptr;
+  }
+  // If this editor is still hiding the caret, we need to restore it.
+  HideCaret(false);
+  mTxnMgr = nullptr;
+
+  delete mPhonetic;
+}
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(EditorBase)
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(EditorBase)
+ NS_IMPL_CYCLE_COLLECTION_UNLINK(mRootElement)
+ NS_IMPL_CYCLE_COLLECTION_UNLINK(mInlineSpellChecker)
+ NS_IMPL_CYCLE_COLLECTION_UNLINK(mTxnMgr)
+ NS_IMPL_CYCLE_COLLECTION_UNLINK(mIMETextNode)
+ NS_IMPL_CYCLE_COLLECTION_UNLINK(mActionListeners)
+ NS_IMPL_CYCLE_COLLECTION_UNLINK(mEditorObservers)
+ NS_IMPL_CYCLE_COLLECTION_UNLINK(mDocStateListeners)
+ NS_IMPL_CYCLE_COLLECTION_UNLINK(mEventTarget)
+ NS_IMPL_CYCLE_COLLECTION_UNLINK(mEventListener)
+ NS_IMPL_CYCLE_COLLECTION_UNLINK(mSavedSel);
+ NS_IMPL_CYCLE_COLLECTION_UNLINK(mRangeUpdater);
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(EditorBase)
+ nsIDocument* currentDoc =
+   tmp->mRootElement ? tmp->mRootElement->GetUncomposedDoc() : nullptr;
+ if (currentDoc &&
+     nsCCUncollectableMarker::InGeneration(cb, currentDoc->GetMarkedCCGeneration())) {
+   return NS_SUCCESS_INTERRUPTED_TRAVERSE;
+ }
+ NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mRootElement)
+ NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mInlineSpellChecker)
+ NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mTxnMgr)
+ NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mIMETextNode)
+ NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mActionListeners)
+ NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mEditorObservers)
+ NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mDocStateListeners)
+ NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mEventTarget)
+ NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mEventListener)
+ NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mSavedSel);
+ NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mRangeUpdater);
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(EditorBase)
+ NS_INTERFACE_MAP_ENTRY(nsIPhonetic)
+ NS_INTERFACE_MAP_ENTRY(nsISupportsWeakReference)
+ NS_INTERFACE_MAP_ENTRY(nsIEditorIMESupport)
+ NS_INTERFACE_MAP_ENTRY(nsIEditor)
+ NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIEditor)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(EditorBase)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(EditorBase)
+
+
+NS_IMETHODIMP
+EditorBase::Init(nsIDOMDocument* aDoc,
+                 nsIContent* aRoot,
+                 nsISelectionController* aSelCon,
+                 uint32_t aFlags,
+                 const nsAString& aValue)
+{
+  MOZ_ASSERT(mAction == EditAction::none,
+             "Initializing during an edit action is an error");
+  MOZ_ASSERT(aDoc);
+  if (!aDoc)
+    return NS_ERROR_NULL_POINTER;
+
+  // First only set flags, but other stuff shouldn't be initialized now.
+  // Don't move this call after initializing mDocWeak.
+  // SetFlags() can check whether it's called during initialization or not by
+  // them.  Note that SetFlags() will be called by PostCreate().
+#ifdef DEBUG
+  nsresult rv =
+#endif
+  SetFlags(aFlags);
+  NS_ASSERTION(NS_SUCCEEDED(rv), "SetFlags() failed");
+
+  mDocWeak = do_GetWeakReference(aDoc);  // weak reference to doc
+  // HTML editors currently don't have their own selection controller,
+  // so they'll pass null as aSelCon, and we'll get the selection controller
+  // off of the presshell.
+  nsCOMPtr<nsISelectionController> selCon;
+  if (aSelCon) {
+    mSelConWeak = do_GetWeakReference(aSelCon);   // weak reference to selectioncontroller
+    selCon = aSelCon;
+  } else {
+    nsCOMPtr<nsIPresShell> presShell = GetPresShell();
+    selCon = do_QueryInterface(presShell);
+  }
+  NS_ASSERTION(selCon, "Selection controller should be available at this point");
+
+  //set up root element if we are passed one.
+  if (aRoot)
+    mRootElement = do_QueryInterface(aRoot);
+
+  mUpdateCount=0;
+
+  // If this is an editor for <input> or <textarea>, mIMETextNode is always
+  // recreated with same content. Therefore, we need to forget mIMETextNode,
+  // but we need to keep storing mIMETextOffset and mIMETextLength becuase
+  // they are necessary to restore IME selection and replacing composing string
+  // when this receives eCompositionChange event next time.
+  if (mIMETextNode && !mIMETextNode->IsInComposedDoc()) {
+    mIMETextNode = nullptr;
+  }
+
+  /* Show the caret */
+  selCon->SetCaretReadOnly(false);
+  selCon->SetDisplaySelection(nsISelectionController::SELECTION_ON);
+
+  selCon->SetSelectionFlags(nsISelectionDisplay::DISPLAY_ALL);//we want to see all the selection reflected to user
+
+  NS_POSTCONDITION(mDocWeak, "bad state");
+
+  // Make sure that the editor will be destroyed properly
+  mDidPreDestroy = false;
+  // Make sure that the ediotr will be created properly
+  mDidPostCreate = false;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::PostCreate()
+{
+  // Synchronize some stuff for the flags.  SetFlags() will initialize
+  // something by the flag difference.  This is first time of that, so, all
+  // initializations must be run.  For such reason, we need to invert mFlags
+  // value first.
+  mFlags = ~mFlags;
+  nsresult rv = SetFlags(~mFlags);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // These operations only need to happen on the first PostCreate call
+  if (!mDidPostCreate) {
+    mDidPostCreate = true;
+
+    // Set up listeners
+    CreateEventListeners();
+    rv = InstallEventListeners();
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    // nuke the modification count, so the doc appears unmodified
+    // do this before we notify listeners
+    ResetModificationCount();
+
+    // update the UI with our state
+    NotifyDocumentListeners(eDocumentCreated);
+    NotifyDocumentListeners(eDocumentStateChanged);
+  }
+
+  // update nsTextStateManager and caret if we have focus
+  nsCOMPtr<nsIContent> focusedContent = GetFocusedContent();
+  if (focusedContent) {
+    nsCOMPtr<nsIDOMEventTarget> target = do_QueryInterface(focusedContent);
+    if (target) {
+      InitializeSelection(target);
+    }
+
+    // If the text control gets reframed during focus, Focus() would not be
+    // called, so take a chance here to see if we need to spell check the text
+    // control.
+    EditorEventListener* listener =
+      reinterpret_cast<EditorEventListener*>(mEventListener.get());
+    listener->SpellCheckIfNeeded();
+
+    IMEState newState;
+    rv = GetPreferredIMEState(&newState);
+    NS_ENSURE_SUCCESS(rv, NS_OK);
+    nsCOMPtr<nsIContent> content = GetFocusedContentForIME();
+    IMEStateManager::UpdateIMEState(newState, content, *this);
+  }
+
+  // FYI: This call might cause destroying this editor.
+  IMEStateManager::OnEditorInitialized(this);
+
+  return NS_OK;
+}
+
+void
+EditorBase::CreateEventListeners()
+{
+  // Don't create the handler twice
+  if (!mEventListener) {
+    mEventListener = new EditorEventListener();
+  }
+}
+
+nsresult
+EditorBase::InstallEventListeners()
+{
+  NS_ENSURE_TRUE(mDocWeak && mEventListener,
+                 NS_ERROR_NOT_INITIALIZED);
+
+  // Initialize the event target.
+  nsCOMPtr<nsIContent> rootContent = GetRoot();
+  NS_ENSURE_TRUE(rootContent, NS_ERROR_NOT_AVAILABLE);
+  mEventTarget = do_QueryInterface(rootContent->GetParent());
+  NS_ENSURE_TRUE(mEventTarget, NS_ERROR_NOT_AVAILABLE);
+
+  EditorEventListener* listener =
+    reinterpret_cast<EditorEventListener*>(mEventListener.get());
+  nsresult rv = listener->Connect(this);
+  if (mComposition) {
+    // Restart to handle composition with new editor contents.
+    mComposition->StartHandlingComposition(this);
+  }
+  return rv;
+}
+
+void
+EditorBase::RemoveEventListeners()
+{
+  if (!mDocWeak || !mEventListener) {
+    return;
+  }
+  reinterpret_cast<EditorEventListener*>(mEventListener.get())->Disconnect();
+  if (mComposition) {
+    // Even if this is called, don't release mComposition because this is
+    // may be reused after reframing.
+    mComposition->EndHandlingComposition(this);
+  }
+  mEventTarget = nullptr;
+}
+
+bool
+EditorBase::GetDesiredSpellCheckState()
+{
+  // Check user override on this element
+  if (mSpellcheckCheckboxState != eTriUnset) {
+    return (mSpellcheckCheckboxState == eTriTrue);
+  }
+
+  // Check user preferences
+  int32_t spellcheckLevel = Preferences::GetInt("layout.spellcheckDefault", 1);
+
+  if (!spellcheckLevel) {
+    return false;                    // Spellchecking forced off globally
+  }
+
+  if (!CanEnableSpellCheck()) {
+    return false;
+  }
+
+  nsCOMPtr<nsIPresShell> presShell = GetPresShell();
+  if (presShell) {
+    nsPresContext* context = presShell->GetPresContext();
+    if (context && !context->IsDynamic()) {
+      return false;
+    }
+  }
+
+  // Check DOM state
+  nsCOMPtr<nsIContent> content = GetExposedRoot();
+  if (!content) {
+    return false;
+  }
+
+  nsCOMPtr<nsIDOMHTMLElement> element = do_QueryInterface(content);
+  if (!element) {
+    return false;
+  }
+
+  if (!IsPlaintextEditor()) {
+    // Some of the page content might be editable and some not, if spellcheck=
+    // is explicitly set anywhere, so if there's anything editable on the page,
+    // return true and let the spellchecker figure it out.
+    nsCOMPtr<nsIHTMLDocument> doc = do_QueryInterface(content->GetUncomposedDoc());
+    return doc && doc->IsEditingOn();
+  }
+
+  bool enable;
+  element->GetSpellcheck(&enable);
+
+  return enable;
+}
+
+NS_IMETHODIMP
+EditorBase::PreDestroy(bool aDestroyingFrames)
+{
+  if (mDidPreDestroy)
+    return NS_OK;
+
+  IMEStateManager::OnEditorDestroying(this);
+
+  // Let spellchecker clean up its observers etc. It is important not to
+  // actually free the spellchecker here, since the spellchecker could have
+  // caused flush notifications, which could have gotten here if a textbox
+  // is being removed. Setting the spellchecker to nullptr could free the
+  // object that is still in use! It will be freed when the editor is
+  // destroyed.
+  if (mInlineSpellChecker)
+    mInlineSpellChecker->Cleanup(aDestroyingFrames);
+
+  // tell our listeners that the doc is going away
+  NotifyDocumentListeners(eDocumentToBeDestroyed);
+
+  // Unregister event listeners
+  RemoveEventListeners();
+  // If this editor is still hiding the caret, we need to restore it.
+  HideCaret(false);
+  mActionListeners.Clear();
+  mEditorObservers.Clear();
+  mDocStateListeners.Clear();
+  mInlineSpellChecker = nullptr;
+  mSpellcheckCheckboxState = eTriUnset;
+  mRootElement = nullptr;
+
+  mDidPreDestroy = true;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::GetFlags(uint32_t* aFlags)
+{
+  *aFlags = mFlags;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::SetFlags(uint32_t aFlags)
+{
+  if (mFlags == aFlags) {
+    return NS_OK;
+  }
+
+  bool spellcheckerWasEnabled = CanEnableSpellCheck();
+  mFlags = aFlags;
+
+  if (!mDocWeak) {
+    // If we're initializing, we shouldn't do anything now.
+    // SetFlags() will be called by PostCreate(),
+    // we should synchronize some stuff for the flags at that time.
+    return NS_OK;
+  }
+
+  // The flag change may cause the spellchecker state change
+  if (CanEnableSpellCheck() != spellcheckerWasEnabled) {
+    nsresult rv = SyncRealTimeSpell();
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  // If this is called from PostCreate(), it will update the IME state if it's
+  // necessary.
+  if (!mDidPostCreate) {
+    return NS_OK;
+  }
+
+  // Might be changing editable state, so, we need to reset current IME state
+  // if we're focused and the flag change causes IME state change.
+  nsCOMPtr<nsIContent> focusedContent = GetFocusedContent();
+  if (focusedContent) {
+    IMEState newState;
+    nsresult rv = GetPreferredIMEState(&newState);
+    if (NS_SUCCEEDED(rv)) {
+      // NOTE: When the enabled state isn't going to be modified, this method
+      // is going to do nothing.
+      nsCOMPtr<nsIContent> content = GetFocusedContentForIME();
+      IMEStateManager::UpdateIMEState(newState, content, *this);
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::GetIsSelectionEditable(bool* aIsSelectionEditable)
+{
+  NS_ENSURE_ARG_POINTER(aIsSelectionEditable);
+
+  // get current selection
+  RefPtr<Selection> selection = GetSelection();
+  NS_ENSURE_TRUE(selection, NS_ERROR_NULL_POINTER);
+
+  // XXX we just check that the anchor node is editable at the moment
+  //     we should check that all nodes in the selection are editable
+  nsCOMPtr<nsINode> anchorNode = selection->GetAnchorNode();
+  *aIsSelectionEditable = anchorNode && IsEditable(anchorNode);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::GetIsDocumentEditable(bool* aIsDocumentEditable)
+{
+  NS_ENSURE_ARG_POINTER(aIsDocumentEditable);
+  nsCOMPtr<nsIDocument> doc = GetDocument();
+  *aIsDocumentEditable = !!doc;
+
+  return NS_OK;
+}
+
+already_AddRefed<nsIDocument>
+EditorBase::GetDocument()
+{
+  NS_PRECONDITION(mDocWeak, "bad state, mDocWeak weak pointer not initialized");
+  nsCOMPtr<nsIDocument> doc = do_QueryReferent(mDocWeak);
+  return doc.forget();
+}
+
+already_AddRefed<nsIDOMDocument>
+EditorBase::GetDOMDocument()
+{
+  NS_PRECONDITION(mDocWeak, "bad state, mDocWeak weak pointer not initialized");
+  nsCOMPtr<nsIDOMDocument> doc = do_QueryReferent(mDocWeak);
+  return doc.forget();
+}
+
+NS_IMETHODIMP
+EditorBase::GetDocument(nsIDOMDocument** aDoc)
+{
+  *aDoc = GetDOMDocument().take();
+  return *aDoc ? NS_OK : NS_ERROR_NOT_INITIALIZED;
+}
+
+already_AddRefed<nsIPresShell>
+EditorBase::GetPresShell()
+{
+  NS_PRECONDITION(mDocWeak, "bad state, null mDocWeak");
+  nsCOMPtr<nsIDocument> doc = do_QueryReferent(mDocWeak);
+  NS_ENSURE_TRUE(doc, nullptr);
+  nsCOMPtr<nsIPresShell> ps = doc->GetShell();
+  return ps.forget();
+}
+
+already_AddRefed<nsIWidget>
+EditorBase::GetWidget()
+{
+  nsCOMPtr<nsIPresShell> ps = GetPresShell();
+  NS_ENSURE_TRUE(ps, nullptr);
+  nsPresContext* pc = ps->GetPresContext();
+  NS_ENSURE_TRUE(pc, nullptr);
+  nsCOMPtr<nsIWidget> widget = pc->GetRootWidget();
+  NS_ENSURE_TRUE(widget.get(), nullptr);
+  return widget.forget();
+}
+
+NS_IMETHODIMP
+EditorBase::GetContentsMIMEType(char** aContentsMIMEType)
+{
+  NS_ENSURE_ARG_POINTER(aContentsMIMEType);
+  *aContentsMIMEType = ToNewCString(mContentMIMEType);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::SetContentsMIMEType(const char* aContentsMIMEType)
+{
+  mContentMIMEType.Assign(aContentsMIMEType ? aContentsMIMEType : "");
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::GetSelectionController(nsISelectionController** aSel)
+{
+  NS_ENSURE_TRUE(aSel, NS_ERROR_NULL_POINTER);
+  *aSel = nullptr; // init out param
+  nsCOMPtr<nsISelectionController> selCon;
+  if (mSelConWeak) {
+    selCon = do_QueryReferent(mSelConWeak);
+  } else {
+    nsCOMPtr<nsIPresShell> presShell = GetPresShell();
+    selCon = do_QueryInterface(presShell);
+  }
+  if (!selCon) {
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+  NS_ADDREF(*aSel = selCon);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::DeleteSelection(EDirection aAction,
+                            EStripWrappers aStripWrappers)
+{
+  MOZ_ASSERT(aStripWrappers == eStrip || aStripWrappers == eNoStrip);
+  return DeleteSelectionImpl(aAction, aStripWrappers);
+}
+
+NS_IMETHODIMP
+EditorBase::GetSelection(nsISelection** aSelection)
+{
+  return GetSelection(SelectionType::eNormal, aSelection);
+}
+
+nsresult
+EditorBase::GetSelection(SelectionType aSelectionType,
+                         nsISelection** aSelection)
+{
+  NS_ENSURE_TRUE(aSelection, NS_ERROR_NULL_POINTER);
+  *aSelection = nullptr;
+  nsCOMPtr<nsISelectionController> selcon;
+  GetSelectionController(getter_AddRefs(selcon));
+  if (!selcon) {
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+  return selcon->GetSelection(ToRawSelectionType(aSelectionType), aSelection);
+}
+
+Selection*
+EditorBase::GetSelection(SelectionType aSelectionType)
+{
+  nsCOMPtr<nsISelection> sel;
+  nsresult rv = GetSelection(aSelectionType, getter_AddRefs(sel));
+  if (NS_WARN_IF(NS_FAILED(rv)) || NS_WARN_IF(!sel)) {
+    return nullptr;
+  }
+
+  return sel->AsSelection();
+}
+
+NS_IMETHODIMP
+EditorBase::DoTransaction(nsITransaction* aTxn)
+{
+  if (mPlaceHolderBatch && !mPlaceHolderTxn) {
+    nsCOMPtr<nsIAbsorbingTransaction> placeholderTransaction =
+      new PlaceholderTransaction();
+
+    // Save off weak reference to placeholder transaction
+    mPlaceHolderTxn = do_GetWeakReference(placeholderTransaction);
+    placeholderTransaction->Init(mPlaceHolderName, mSelState, this);
+    // placeholder txn took ownership of this pointer
+    mSelState = nullptr;
+
+    // QI to an nsITransaction since that's what DoTransaction() expects
+    nsCOMPtr<nsITransaction> transaction =
+      do_QueryInterface(placeholderTransaction);
+    // We will recurse, but will not hit this case in the nested call
+    DoTransaction(transaction);
+
+    if (mTxnMgr) {
+      nsCOMPtr<nsITransaction> topTxn = mTxnMgr->PeekUndoStack();
+      if (topTxn) {
+        placeholderTransaction = do_QueryInterface(topTxn);
+        if (placeholderTransaction) {
+          // there is a placeholder transaction on top of the undo stack.  It
+          // is either the one we just created, or an earlier one that we are
+          // now merging into.  From here on out remember this placeholder
+          // instead of the one we just created.
+          mPlaceHolderTxn = do_GetWeakReference(placeholderTransaction);
+        }
+      }
+    }
+  }
+
+  if (aTxn) {
+    // XXX: Why are we doing selection specific batching stuff here?
+    // XXX: Most entry points into the editor have auto variables that
+    // XXX: should trigger Begin/EndUpdateViewBatch() calls that will make
+    // XXX: these selection batch calls no-ops.
+    // XXX:
+    // XXX: I suspect that this was placed here to avoid multiple
+    // XXX: selection changed notifications from happening until after
+    // XXX: the transaction was done. I suppose that can still happen
+    // XXX: if an embedding application called DoTransaction() directly
+    // XXX: to pump its own transactions through the system, but in that
+    // XXX: case, wouldn't we want to use Begin/EndUpdateViewBatch() or
+    // XXX: its auto equivalent AutoUpdateViewBatch to ensure that
+    // XXX: selection listeners have access to accurate frame data?
+    // XXX:
+    // XXX: Note that if we did add Begin/EndUpdateViewBatch() calls
+    // XXX: we will need to make sure that they are disabled during
+    // XXX: the init of the editor for text widgets to avoid layout
+    // XXX: re-entry during initial reflow. - kin
+
+    // get the selection and start a batch change
+    RefPtr<Selection> selection = GetSelection();
+    NS_ENSURE_TRUE(selection, NS_ERROR_NULL_POINTER);
+
+    selection->StartBatchChanges();
+
+    nsresult rv;
+    if (mTxnMgr) {
+      RefPtr<nsTransactionManager> txnMgr = mTxnMgr;
+      rv = txnMgr->DoTransaction(aTxn);
+    } else {
+      rv = aTxn->DoTransaction();
+    }
+    if (NS_SUCCEEDED(rv)) {
+      DoAfterDoTransaction(aTxn);
+    }
+
+    // no need to check rv here, don't lose result of operation
+    selection->EndBatchChanges();
+
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::EnableUndo(bool aEnable)
+{
+  if (aEnable) {
+    if (!mTxnMgr) {
+      mTxnMgr = new nsTransactionManager();
+    }
+    mTxnMgr->SetMaxTransactionCount(-1);
+  } else if (mTxnMgr) {
+    // disable the transaction manager if it is enabled
+    mTxnMgr->Clear();
+    mTxnMgr->SetMaxTransactionCount(0);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::GetNumberOfUndoItems(int32_t* aNumItems)
+{
+  *aNumItems = 0;
+  return mTxnMgr ? mTxnMgr->GetNumberOfUndoItems(aNumItems) : NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::GetNumberOfRedoItems(int32_t* aNumItems)
+{
+  *aNumItems = 0;
+  return mTxnMgr ? mTxnMgr->GetNumberOfRedoItems(aNumItems) : NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::GetTransactionManager(nsITransactionManager** aTxnManager)
+{
+  NS_ENSURE_ARG_POINTER(aTxnManager);
+
+  *aTxnManager = nullptr;
+  NS_ENSURE_TRUE(mTxnMgr, NS_ERROR_FAILURE);
+
+  NS_ADDREF(*aTxnManager = mTxnMgr);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::SetTransactionManager(nsITransactionManager* aTxnManager)
+{
+  NS_ENSURE_TRUE(aTxnManager, NS_ERROR_FAILURE);
+
+  // nsITransactionManager is builtinclass, so this is safe
+  mTxnMgr = static_cast<nsTransactionManager*>(aTxnManager);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::Undo(uint32_t aCount)
+{
+  ForceCompositionEnd();
+
+  bool hasTxnMgr, hasTransaction = false;
+  CanUndo(&hasTxnMgr, &hasTransaction);
+  NS_ENSURE_TRUE(hasTransaction, NS_OK);
+
+  AutoRules beginRulesSniffing(this, EditAction::undo, nsIEditor::eNone);
+
+  if (!mTxnMgr) {
+    return NS_OK;
+  }
+
+  RefPtr<nsTransactionManager> txnMgr = mTxnMgr;
+  for (uint32_t i = 0; i < aCount; ++i) {
+    nsresult rv = txnMgr->UndoTransaction();
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    DoAfterUndoTransaction();
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::CanUndo(bool* aIsEnabled,
+                    bool* aCanUndo)
+{
+  NS_ENSURE_TRUE(aIsEnabled && aCanUndo, NS_ERROR_NULL_POINTER);
+  *aIsEnabled = !!mTxnMgr;
+  if (*aIsEnabled) {
+    int32_t numTxns = 0;
+    mTxnMgr->GetNumberOfUndoItems(&numTxns);
+    *aCanUndo = !!numTxns;
+  } else {
+    *aCanUndo = false;
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::Redo(uint32_t aCount)
+{
+  bool hasTxnMgr, hasTransaction = false;
+  CanRedo(&hasTxnMgr, &hasTransaction);
+  NS_ENSURE_TRUE(hasTransaction, NS_OK);
+
+  AutoRules beginRulesSniffing(this, EditAction::redo, nsIEditor::eNone);
+
+  if (!mTxnMgr) {
+    return NS_OK;
+  }
+
+  RefPtr<nsTransactionManager> txnMgr = mTxnMgr;
+  for (uint32_t i = 0; i < aCount; ++i) {
+    nsresult rv = txnMgr->RedoTransaction();
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    DoAfterRedoTransaction();
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::CanRedo(bool* aIsEnabled, bool* aCanRedo)
+{
+  NS_ENSURE_TRUE(aIsEnabled && aCanRedo, NS_ERROR_NULL_POINTER);
+
+  *aIsEnabled = !!mTxnMgr;
+  if (*aIsEnabled) {
+    int32_t numTxns = 0;
+    mTxnMgr->GetNumberOfRedoItems(&numTxns);
+    *aCanRedo = !!numTxns;
+  } else {
+    *aCanRedo = false;
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::BeginTransaction()
+{
+  BeginUpdateViewBatch();
+
+  if (mTxnMgr) {
+    RefPtr<nsTransactionManager> txnMgr = mTxnMgr;
+    txnMgr->BeginBatch(nullptr);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::EndTransaction()
+{
+  if (mTxnMgr) {
+    RefPtr<nsTransactionManager> txnMgr = mTxnMgr;
+    txnMgr->EndBatch(false);
+  }
+
+  EndUpdateViewBatch();
+
+  return NS_OK;
+}
+
+
+// These two routines are similar to the above, but do not use
+// the transaction managers batching feature.  Instead we use
+// a placeholder transaction to wrap up any further transaction
+// while the batch is open.  The advantage of this is that
+// placeholder transactions can later merge, if needed.  Merging
+// is unavailable between transaction manager batches.
+
+NS_IMETHODIMP
+EditorBase::BeginPlaceHolderTransaction(nsIAtom* aName)
+{
+  NS_PRECONDITION(mPlaceHolderBatch >= 0, "negative placeholder batch count!");
+  if (!mPlaceHolderBatch) {
+    NotifyEditorObservers(eNotifyEditorObserversOfBefore);
+    // time to turn on the batch
+    BeginUpdateViewBatch();
+    mPlaceHolderTxn = nullptr;
+    mPlaceHolderName = aName;
+    RefPtr<Selection> selection = GetSelection();
+    if (selection) {
+      mSelState = new SelectionState();
+      mSelState->SaveSelection(selection);
+      // Composition transaction can modify multiple nodes and it merges text
+      // node for ime into single text node.
+      // So if current selection is into IME text node, it might be failed
+      // to restore selection by UndoTransaction.
+      // So we need update selection by range updater.
+      if (mPlaceHolderName == nsGkAtoms::IMETxnName) {
+        mRangeUpdater.RegisterSelectionState(*mSelState);
+      }
+    }
+  }
+  mPlaceHolderBatch++;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::EndPlaceHolderTransaction()
+{
+  NS_PRECONDITION(mPlaceHolderBatch > 0, "zero or negative placeholder batch count when ending batch!");
+  if (mPlaceHolderBatch == 1) {
+    RefPtr<Selection> selection = GetSelection();
+
+    // By making the assumption that no reflow happens during the calls
+    // to EndUpdateViewBatch and ScrollSelectionIntoView, we are able to
+    // allow the selection to cache a frame offset which is used by the
+    // caret drawing code. We only enable this cache here; at other times,
+    // we have no way to know whether reflow invalidates it
+    // See bugs 35296 and 199412.
+    if (selection) {
+      selection->SetCanCacheFrameOffset(true);
+    }
+
+    {
+      // Hide the caret here to avoid hiding it twice, once in EndUpdateViewBatch
+      // and once in ScrollSelectionIntoView.
+      RefPtr<nsCaret> caret;
+      nsCOMPtr<nsIPresShell> presShell = GetPresShell();
+
+      if (presShell) {
+        caret = presShell->GetCaret();
+      }
+
+      // time to turn off the batch
+      EndUpdateViewBatch();
+      // make sure selection is in view
+
+      // After ScrollSelectionIntoView(), the pending notifications might be
+      // flushed and PresShell/PresContext/Frames may be dead. See bug 418470.
+      ScrollSelectionIntoView(false);
+    }
+
+    // cached for frame offset are Not available now
+    if (selection) {
+      selection->SetCanCacheFrameOffset(false);
+    }
+
+    if (mSelState) {
+      // we saved the selection state, but never got to hand it to placeholder
+      // (else we ould have nulled out this pointer), so destroy it to prevent leaks.
+      if (mPlaceHolderName == nsGkAtoms::IMETxnName) {
+        mRangeUpdater.DropSelectionState(*mSelState);
+      }
+      delete mSelState;
+      mSelState = nullptr;
+    }
+    // We might have never made a placeholder if no action took place.
+    if (mPlaceHolderTxn) {
+      nsCOMPtr<nsIAbsorbingTransaction> plcTxn = do_QueryReferent(mPlaceHolderTxn);
+      if (plcTxn) {
+        plcTxn->EndPlaceHolderBatch();
+      } else {
+        // in the future we will check to make sure undo is off here,
+        // since that is the only known case where the placeholdertxn would disappear on us.
+        // For now just removing the assert.
+      }
+      // notify editor observers of action but if composing, it's done by
+      // compositionchange event handler.
+      if (!mComposition) {
+        NotifyEditorObservers(eNotifyEditorObserversOfEnd);
+      }
+    } else {
+      NotifyEditorObservers(eNotifyEditorObserversOfCancel);
+    }
+  }
+  mPlaceHolderBatch--;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::ShouldTxnSetSelection(bool* aResult)
+{
+  NS_ENSURE_TRUE(aResult, NS_ERROR_NULL_POINTER);
+  *aResult = mShouldTxnSetSelection;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::SetShouldTxnSetSelection(bool aShould)
+{
+  mShouldTxnSetSelection = aShould;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::GetDocumentIsEmpty(bool* aDocumentIsEmpty)
+{
+  *aDocumentIsEmpty = true;
+
+  dom::Element* root = GetRoot();
+  NS_ENSURE_TRUE(root, NS_ERROR_NULL_POINTER);
+
+  *aDocumentIsEmpty = !root->HasChildren();
+  return NS_OK;
+}
+
+// XXX: The rule system should tell us which node to select all on (ie, the
+//      root, or the body)
+NS_IMETHODIMP
+EditorBase::SelectAll()
+{
+  if (!mDocWeak) {
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+  ForceCompositionEnd();
+
+  RefPtr<Selection> selection = GetSelection();
+  NS_ENSURE_TRUE(selection, NS_ERROR_NOT_INITIALIZED);
+  return SelectEntireDocument(selection);
+}
+
+NS_IMETHODIMP
+EditorBase::BeginningOfDocument()
+{
+  if (!mDocWeak) {
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+
+  // get the selection
+  RefPtr<Selection> selection = GetSelection();
+  NS_ENSURE_TRUE(selection, NS_ERROR_NOT_INITIALIZED);
+
+  // get the root element
+  dom::Element* rootElement = GetRoot();
+  NS_ENSURE_TRUE(rootElement, NS_ERROR_NULL_POINTER);
+
+  // find first editable thingy
+  nsCOMPtr<nsINode> firstNode = GetFirstEditableNode(rootElement);
+  if (!firstNode) {
+    // just the root node, set selection to inside the root
+    return selection->CollapseNative(rootElement, 0);
+  }
+
+  if (firstNode->NodeType() == nsIDOMNode::TEXT_NODE) {
+    // If firstNode is text, set selection to beginning of the text node.
+    return selection->CollapseNative(firstNode, 0);
+  }
+
+  // Otherwise, it's a leaf node and we set the selection just in front of it.
+  nsCOMPtr<nsIContent> parent = firstNode->GetParent();
+  if (!parent) {
+    return NS_ERROR_NULL_POINTER;
+  }
+
+  int32_t offsetInParent = parent->IndexOf(firstNode);
+  return selection->CollapseNative(parent, offsetInParent);
+}
+
+NS_IMETHODIMP
+EditorBase::EndOfDocument()
+{
+  NS_ENSURE_TRUE(mDocWeak, NS_ERROR_NOT_INITIALIZED);
+
+  // get selection
+  RefPtr<Selection> selection = GetSelection();
+  NS_ENSURE_TRUE(selection, NS_ERROR_NULL_POINTER);
+
+  // get the root element
+  nsINode* node = GetRoot();
+  NS_ENSURE_TRUE(node, NS_ERROR_NULL_POINTER);
+  nsINode* child = node->GetLastChild();
+
+  while (child && IsContainer(child->AsDOMNode())) {
+    node = child;
+    child = node->GetLastChild();
+  }
+
+  uint32_t length = node->Length();
+  return selection->CollapseNative(node, int32_t(length));
+}
+
+NS_IMETHODIMP
+EditorBase::GetDocumentModified(bool* outDocModified)
+{
+  NS_ENSURE_TRUE(outDocModified, NS_ERROR_NULL_POINTER);
+
+  int32_t  modCount = 0;
+  GetModificationCount(&modCount);
+
+  *outDocModified = (modCount != 0);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::GetDocumentCharacterSet(nsACString& characterSet)
+{
+  nsCOMPtr<nsIDocument> doc = do_QueryReferent(mDocWeak);
+  NS_ENSURE_TRUE(doc, NS_ERROR_UNEXPECTED);
+
+  characterSet = doc->GetDocumentCharacterSet();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::SetDocumentCharacterSet(const nsACString& characterSet)
+{
+  nsCOMPtr<nsIDocument> doc = do_QueryReferent(mDocWeak);
+  NS_ENSURE_TRUE(doc, NS_ERROR_UNEXPECTED);
+
+  doc->SetDocumentCharacterSet(characterSet);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::Cut()
+{
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+EditorBase::CanCut(bool* aCanCut)
+{
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+EditorBase::Copy()
+{
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+EditorBase::CanCopy(bool* aCanCut)
+{
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+EditorBase::CanDelete(bool* aCanDelete)
+{
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+EditorBase::Paste(int32_t aSelectionType)
+{
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+EditorBase::PasteTransferable(nsITransferable* aTransferable)
+{
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+EditorBase::CanPaste(int32_t aSelectionType, bool* aCanPaste)
+{
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+EditorBase::CanPasteTransferable(nsITransferable* aTransferable,
+                                 bool* aCanPaste)
+{
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+EditorBase::SetAttribute(nsIDOMElement* aElement,
+                         const nsAString& aAttribute,
+                         const nsAString& aValue)
+{
+  nsCOMPtr<Element> element = do_QueryInterface(aElement);
+  NS_ENSURE_TRUE(element, NS_ERROR_NULL_POINTER);
+  nsCOMPtr<nsIAtom> attribute = NS_Atomize(aAttribute);
+
+  RefPtr<ChangeAttributeTransaction> transaction =
+    CreateTxnForSetAttribute(*element, *attribute, aValue);
+  return DoTransaction(transaction);
+}
+
+NS_IMETHODIMP
+EditorBase::GetAttributeValue(nsIDOMElement* aElement,
+                              const nsAString& aAttribute,
+                              nsAString& aResultValue,
+                              bool* aResultIsSet)
+{
+  NS_ENSURE_TRUE(aResultIsSet, NS_ERROR_NULL_POINTER);
+  *aResultIsSet = false;
+  if (!aElement) {
+    return NS_OK;
+  }
+  nsAutoString value;
+  nsresult rv = aElement->GetAttribute(aAttribute, value);
+  NS_ENSURE_SUCCESS(rv, rv);
+  if (!DOMStringIsNull(value)) {
+    *aResultIsSet = true;
+    aResultValue = value;
+  }
+  return rv;
+}
+
+NS_IMETHODIMP
+EditorBase::RemoveAttribute(nsIDOMElement* aElement,
+                            const nsAString& aAttribute)
+{
+  nsCOMPtr<Element> element = do_QueryInterface(aElement);
+  NS_ENSURE_TRUE(element, NS_ERROR_NULL_POINTER);
+  nsCOMPtr<nsIAtom> attribute = NS_Atomize(aAttribute);
+
+  RefPtr<ChangeAttributeTransaction> transaction =
+    CreateTxnForRemoveAttribute(*element, *attribute);
+  return DoTransaction(transaction);
+}
+
+bool
+EditorBase::OutputsMozDirty()
+{
+  // Return true for Composer (!eEditorAllowInteraction) or mail
+  // (eEditorMailMask), but false for webpages.
+  return !(mFlags & nsIPlaintextEditor::eEditorAllowInteraction) ||
+          (mFlags & nsIPlaintextEditor::eEditorMailMask);
+}
+
+NS_IMETHODIMP
+EditorBase::MarkNodeDirty(nsIDOMNode* aNode)
+{
+  // Mark the node dirty, but not for webpages (bug 599983)
+  if (!OutputsMozDirty()) {
+    return NS_OK;
+  }
+  nsCOMPtr<dom::Element> element = do_QueryInterface(aNode);
+  if (element) {
+    element->SetAttr(kNameSpaceID_None, nsGkAtoms::mozdirty,
+                     EmptyString(), false);
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::GetInlineSpellChecker(bool autoCreate,
+                                  nsIInlineSpellChecker** aInlineSpellChecker)
+{
+  NS_ENSURE_ARG_POINTER(aInlineSpellChecker);
+
+  if (mDidPreDestroy) {
+    // Don't allow people to get or create the spell checker once the editor
+    // is going away.
+    *aInlineSpellChecker = nullptr;
+    return autoCreate ? NS_ERROR_NOT_AVAILABLE : NS_OK;
+  }
+
+  // We don't want to show the spell checking UI if there are no spell check dictionaries available.
+  bool canSpell = mozInlineSpellChecker::CanEnableInlineSpellChecking();
+  if (!canSpell) {
+    *aInlineSpellChecker = nullptr;
+    return NS_ERROR_FAILURE;
+  }
+
+  nsresult rv;
+  if (!mInlineSpellChecker && autoCreate) {
+    mInlineSpellChecker = do_CreateInstance(MOZ_INLINESPELLCHECKER_CONTRACTID, &rv);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  if (mInlineSpellChecker) {
+    rv = mInlineSpellChecker->Init(this);
+    if (NS_FAILED(rv)) {
+      mInlineSpellChecker = nullptr;
+    }
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  NS_IF_ADDREF(*aInlineSpellChecker = mInlineSpellChecker);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::SyncRealTimeSpell()
+{
+  bool enable = GetDesiredSpellCheckState();
+
+  // Initializes mInlineSpellChecker
+  nsCOMPtr<nsIInlineSpellChecker> spellChecker;
+  GetInlineSpellChecker(enable, getter_AddRefs(spellChecker));
+
+  if (mInlineSpellChecker) {
+    // We might have a mInlineSpellChecker even if there are no dictionaries
+    // available since we don't destroy the mInlineSpellChecker when the last
+    // dictionariy is removed, but in that case spellChecker is null
+    mInlineSpellChecker->SetEnableRealTimeSpell(enable && spellChecker);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::SetSpellcheckUserOverride(bool enable)
+{
+  mSpellcheckCheckboxState = enable ? eTriTrue : eTriFalse;
+
+  return SyncRealTimeSpell();
+}
+
+NS_IMETHODIMP
+EditorBase::CreateNode(const nsAString& aTag,
+                       nsIDOMNode* aParent,
+                       int32_t aPosition,
+                       nsIDOMNode** aNewNode)
+{
+  nsCOMPtr<nsIAtom> tag = NS_Atomize(aTag);
+  nsCOMPtr<nsINode> parent = do_QueryInterface(aParent);
+  NS_ENSURE_STATE(parent);
+  *aNewNode = GetAsDOMNode(CreateNode(tag, parent, aPosition).take());
+  NS_ENSURE_STATE(*aNewNode);
+  return NS_OK;
+}
+
+already_AddRefed<Element>
+EditorBase::CreateNode(nsIAtom* aTag,
+                       nsINode* aParent,
+                       int32_t aPosition)
+{
+  MOZ_ASSERT(aTag && aParent);
+
+  AutoRules beginRulesSniffing(this, EditAction::createNode, nsIEditor::eNext);
+
+  for (auto& listener : mActionListeners) {
+    listener->WillCreateNode(nsDependentAtomString(aTag),
+                             GetAsDOMNode(aParent), aPosition);
+  }
+
+  nsCOMPtr<Element> ret;
+
+  RefPtr<CreateElementTransaction> transaction =
+    CreateTxnForCreateElement(*aTag, *aParent, aPosition);
+  nsresult rv = DoTransaction(transaction);
+  if (NS_SUCCEEDED(rv)) {
+    ret = transaction->GetNewNode();
+    MOZ_ASSERT(ret);
+  }
+
+  mRangeUpdater.SelAdjCreateNode(aParent, aPosition);
+
+  for (auto& listener : mActionListeners) {
+    listener->DidCreateNode(nsDependentAtomString(aTag), GetAsDOMNode(ret),
+                            GetAsDOMNode(aParent), aPosition, rv);
+  }
+
+  return ret.forget();
+}
+
+NS_IMETHODIMP
+EditorBase::InsertNode(nsIDOMNode* aNode,
+                       nsIDOMNode* aParent,
+                       int32_t aPosition)
+{
+  nsCOMPtr<nsIContent> node = do_QueryInterface(aNode);
+  nsCOMPtr<nsINode> parent = do_QueryInterface(aParent);
+  NS_ENSURE_TRUE(node && parent, NS_ERROR_NULL_POINTER);
+
+  return InsertNode(*node, *parent, aPosition);
+}
+
+nsresult
+EditorBase::InsertNode(nsIContent& aNode,
+                       nsINode& aParent,
+                       int32_t aPosition)
+{
+  AutoRules beginRulesSniffing(this, EditAction::insertNode, nsIEditor::eNext);
+
+  for (auto& listener : mActionListeners) {
+    listener->WillInsertNode(aNode.AsDOMNode(), aParent.AsDOMNode(),
+                             aPosition);
+  }
+
+  RefPtr<InsertNodeTransaction> transaction =
+    CreateTxnForInsertNode(aNode, aParent, aPosition);
+  nsresult rv = DoTransaction(transaction);
+
+  mRangeUpdater.SelAdjInsertNode(aParent.AsDOMNode(), aPosition);
+
+  for (auto& listener : mActionListeners) {
+    listener->DidInsertNode(aNode.AsDOMNode(), aParent.AsDOMNode(), aPosition,
+                            rv);
+  }
+
+  return rv;
+}
+
+NS_IMETHODIMP
+EditorBase::SplitNode(nsIDOMNode* aNode,
+                      int32_t aOffset,
+                      nsIDOMNode** aNewLeftNode)
+{
+  nsCOMPtr<nsIContent> node = do_QueryInterface(aNode);
+  NS_ENSURE_STATE(node);
+  ErrorResult rv;
+  nsCOMPtr<nsIContent> newNode = SplitNode(*node, aOffset, rv);
+  *aNewLeftNode = GetAsDOMNode(newNode.forget().take());
+  return rv.StealNSResult();
+}
+
+nsIContent*
+EditorBase::SplitNode(nsIContent& aNode,
+                      int32_t aOffset,
+                      ErrorResult& aResult)
+{
+  AutoRules beginRulesSniffing(this, EditAction::splitNode, nsIEditor::eNext);
+
+  for (auto& listener : mActionListeners) {
+    listener->WillSplitNode(aNode.AsDOMNode(), aOffset);
+  }
+
+  RefPtr<SplitNodeTransaction> transaction =
+    CreateTxnForSplitNode(aNode, aOffset);
+  aResult = DoTransaction(transaction);
+
+  nsCOMPtr<nsIContent> newNode = aResult.Failed() ? nullptr
+                                                  : transaction->GetNewNode();
+
+  mRangeUpdater.SelAdjSplitNode(aNode, aOffset, newNode);
+
+  nsresult rv = aResult.StealNSResult();
+  for (auto& listener : mActionListeners) {
+    listener->DidSplitNode(aNode.AsDOMNode(), aOffset, GetAsDOMNode(newNode),
+                           rv);
+  }
+  // Note: result might be a success code, so we can't use Throw() to
+  // set it on aResult.
+  aResult = rv;
+
+  return newNode;
+}
+
+NS_IMETHODIMP
+EditorBase::JoinNodes(nsIDOMNode* aLeftNode,
+                      nsIDOMNode* aRightNode,
+                      nsIDOMNode*)
+{
+  nsCOMPtr<nsINode> leftNode = do_QueryInterface(aLeftNode);
+  nsCOMPtr<nsINode> rightNode = do_QueryInterface(aRightNode);
+  NS_ENSURE_STATE(leftNode && rightNode && leftNode->GetParentNode());
+  return JoinNodes(*leftNode, *rightNode);
+}
+
+nsresult
+EditorBase::JoinNodes(nsINode& aLeftNode,
+                      nsINode& aRightNode)
+{
+  nsCOMPtr<nsINode> parent = aLeftNode.GetParentNode();
+  MOZ_ASSERT(parent);
+
+  AutoRules beginRulesSniffing(this, EditAction::joinNode,
+                               nsIEditor::ePrevious);
+
+  // Remember some values; later used for saved selection updating.
+  // Find the offset between the nodes to be joined.
+  int32_t offset = parent->IndexOf(&aRightNode);
+  // Find the number of children of the lefthand node
+  uint32_t oldLeftNodeLen = aLeftNode.Length();
+
+  for (auto& listener : mActionListeners) {
+    listener->WillJoinNodes(aLeftNode.AsDOMNode(), aRightNode.AsDOMNode(),
+                            parent->AsDOMNode());
+  }
+
+  nsresult rv = NS_OK;
+  RefPtr<JoinNodeTransaction> transaction =
+    CreateTxnForJoinNode(aLeftNode, aRightNode);
+  if (transaction)  {
+    rv = DoTransaction(transaction);
+  }
+
+  mRangeUpdater.SelAdjJoinNodes(aLeftNode, aRightNode, *parent, offset,
+                                (int32_t)oldLeftNodeLen);
+
+  for (auto& listener : mActionListeners) {
+    listener->DidJoinNodes(aLeftNode.AsDOMNode(), aRightNode.AsDOMNode(),
+                           parent->AsDOMNode(), rv);
+  }
+
+  return rv;
+}
+
+NS_IMETHODIMP
+EditorBase::DeleteNode(nsIDOMNode* aNode)
+{
+  nsCOMPtr<nsINode> node = do_QueryInterface(aNode);
+  NS_ENSURE_STATE(node);
+  return DeleteNode(node);
+}
+
+nsresult
+EditorBase::DeleteNode(nsINode* aNode)
+{
+  AutoRules beginRulesSniffing(this, EditAction::createNode,
+                               nsIEditor::ePrevious);
+
+  // save node location for selection updating code.
+  for (auto& listener : mActionListeners) {
+    listener->WillDeleteNode(aNode->AsDOMNode());
+  }
+
+  RefPtr<DeleteNodeTransaction> transaction;
+  nsresult rv = CreateTxnForDeleteNode(aNode, getter_AddRefs(transaction));
+  if (NS_SUCCEEDED(rv))  {
+    rv = DoTransaction(transaction);
+  }
+
+  for (auto& listener : mActionListeners) {
+    listener->DidDeleteNode(aNode->AsDOMNode(), rv);
+  }
+
+  NS_ENSURE_SUCCESS(rv, rv);
+  return NS_OK;
+}
+
+/**
+ * ReplaceContainer() replaces inNode with a new node (outNode) which is
+ * constructed to be of type aNodeType.  Put inNodes children into outNode.
+ * Callers responsibility to make sure inNode's children can go in outNode.
+ */
+already_AddRefed<Element>
+EditorBase::ReplaceContainer(Element* aOldContainer,
+                             nsIAtom* aNodeType,
+                             nsIAtom* aAttribute,
+                             const nsAString* aValue,
+                             ECloneAttributes aCloneAttributes)
+{
+  MOZ_ASSERT(aOldContainer && aNodeType);
+
+  nsCOMPtr<nsIContent> parent = aOldContainer->GetParent();
+  NS_ENSURE_TRUE(parent, nullptr);
+
+  int32_t offset = parent->IndexOf(aOldContainer);
+
+  // create new container
+  nsCOMPtr<Element> ret = CreateHTMLContent(aNodeType);
+  NS_ENSURE_TRUE(ret, nullptr);
+
+  // set attribute if needed
+  if (aAttribute && aValue && aAttribute != nsGkAtoms::_empty) {
+    nsresult rv = ret->SetAttr(kNameSpaceID_None, aAttribute, *aValue, true);
+    NS_ENSURE_SUCCESS(rv, nullptr);
+  }
+  if (aCloneAttributes == eCloneAttributes) {
+    CloneAttributes(ret, aOldContainer);
+  }
+
+  // notify our internal selection state listener
+  // (Note: An AutoSelectionRestorer object must be created
+  //  before calling this to initialize mRangeUpdater)
+  AutoReplaceContainerSelNotify selStateNotify(mRangeUpdater, aOldContainer,
+                                               ret);
+  {
+    AutoTransactionsConserveSelection conserveSelection(this);
+    while (aOldContainer->HasChildren()) {
+      nsCOMPtr<nsIContent> child = aOldContainer->GetFirstChild();
+
+      nsresult rv = DeleteNode(child);
+      NS_ENSURE_SUCCESS(rv, nullptr);
+
+      rv = InsertNode(*child, *ret, -1);
+      NS_ENSURE_SUCCESS(rv, nullptr);
+    }
+  }
+
+  // insert new container into tree
+  nsresult rv = InsertNode(*ret, *parent, offset);
+  NS_ENSURE_SUCCESS(rv, nullptr);
+
+  // delete old container
+  rv = DeleteNode(aOldContainer);
+  NS_ENSURE_SUCCESS(rv, nullptr);
+
+  return ret.forget();
+}
+
+/**
+ * RemoveContainer() removes inNode, reparenting its children (if any) into the
+ * parent of inNode.
+ */
+nsresult
+EditorBase::RemoveContainer(nsIContent* aNode)
+{
+  MOZ_ASSERT(aNode);
+
+  nsCOMPtr<nsINode> parent = aNode->GetParentNode();
+  NS_ENSURE_STATE(parent);
+
+  int32_t offset = parent->IndexOf(aNode);
+
+  // Loop through the children of inNode and promote them into inNode's parent
+  uint32_t nodeOrigLen = aNode->GetChildCount();
+
+  // notify our internal selection state listener
+  AutoRemoveContainerSelNotify selNotify(mRangeUpdater, aNode, parent,
+                                         offset, nodeOrigLen);
+
+  while (aNode->HasChildren()) {
+    nsCOMPtr<nsIContent> child = aNode->GetLastChild();
+    nsresult rv = DeleteNode(child);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    rv = InsertNode(*child, *parent, offset);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  return DeleteNode(aNode);
+}
+
+/**
+ * InsertContainerAbove() inserts a new parent for inNode, which is contructed
+ * to be of type aNodeType.  outNode becomes a child of inNode's earlier
+ * parent.  Caller's responsibility to make sure inNode's can be child of
+ * outNode, and outNode can be child of old parent.
+ */
+already_AddRefed<Element>
+EditorBase::InsertContainerAbove(nsIContent* aNode,
+                                 nsIAtom* aNodeType,
+                                 nsIAtom* aAttribute,
+                                 const nsAString* aValue)
+{
+  MOZ_ASSERT(aNode && aNodeType);
+
+  nsCOMPtr<nsIContent> parent = aNode->GetParent();
+  NS_ENSURE_TRUE(parent, nullptr);
+  int32_t offset = parent->IndexOf(aNode);
+
+  // Create new container
+  nsCOMPtr<Element> newContent = CreateHTMLContent(aNodeType);
+  NS_ENSURE_TRUE(newContent, nullptr);
+
+  // Set attribute if needed
+  if (aAttribute && aValue && aAttribute != nsGkAtoms::_empty) {
+    nsresult rv =
+      newContent->SetAttr(kNameSpaceID_None, aAttribute, *aValue, true);
+    NS_ENSURE_SUCCESS(rv, nullptr);
+  }
+
+  // Notify our internal selection state listener
+  AutoInsertContainerSelNotify selNotify(mRangeUpdater);
+
+  // Put inNode in new parent, outNode
+  nsresult rv = DeleteNode(aNode);
+  NS_ENSURE_SUCCESS(rv, nullptr);
+
+  {
+    AutoTransactionsConserveSelection conserveSelection(this);
+    rv = InsertNode(*aNode, *newContent, 0);
+    NS_ENSURE_SUCCESS(rv, nullptr);
+  }
+
+  // Put new parent in doc
+  rv = InsertNode(*newContent, *parent, offset);
+  NS_ENSURE_SUCCESS(rv, nullptr);
+
+  return newContent.forget();
+}
+
+/**
+ * MoveNode() moves aNode to {aParent,aOffset}.
+ */
+nsresult
+EditorBase::MoveNode(nsIContent* aNode,
+                     nsINode* aParent,
+                     int32_t aOffset)
+{
+  MOZ_ASSERT(aNode);
+  MOZ_ASSERT(aParent);
+  MOZ_ASSERT(aOffset == -1 ||
+             (0 <= aOffset &&
+              AssertedCast<uint32_t>(aOffset) <= aParent->Length()));
+
+  nsCOMPtr<nsINode> oldParent = aNode->GetParentNode();
+  int32_t oldOffset = oldParent ? oldParent->IndexOf(aNode) : -1;
+
+  if (aOffset == -1) {
+    // Magic value meaning "move to end of aParent"
+    aOffset = AssertedCast<int32_t>(aParent->Length());
+  }
+
+  // Don't do anything if it's already in right place
+  if (aParent == oldParent && aOffset == oldOffset) {
+    return NS_OK;
+  }
+
+  // Notify our internal selection state listener
+  AutoMoveNodeSelNotify selNotify(mRangeUpdater, oldParent, oldOffset,
+                                  aParent, aOffset);
+
+  // Need to adjust aOffset if we're moving aNode later in its current parent
+  if (aParent == oldParent && oldOffset < aOffset) {
+    // When we delete aNode, it will make the offsets after it off by one
+    aOffset--;
+  }
+
+  // Hold a reference so aNode doesn't go away when we remove it (bug 772282)
+  nsCOMPtr<nsINode> kungFuDeathGrip = aNode;
+
+  nsresult rv = DeleteNode(aNode);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return InsertNode(*aNode, *aParent, aOffset);
+}
+
+NS_IMETHODIMP
+EditorBase::AddEditorObserver(nsIEditorObserver* aObserver)
+{
+  // we don't keep ownership of the observers.  They must
+  // remove themselves as observers before they are destroyed.
+
+  NS_ENSURE_TRUE(aObserver, NS_ERROR_NULL_POINTER);
+
+  // Make sure the listener isn't already on the list
+  if (!mEditorObservers.Contains(aObserver)) {
+    mEditorObservers.AppendElement(*aObserver);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::RemoveEditorObserver(nsIEditorObserver* aObserver)
+{
+  NS_ENSURE_TRUE(aObserver, NS_ERROR_FAILURE);
+
+  mEditorObservers.RemoveElement(aObserver);
+
+  return NS_OK;
+}
+
+class EditorInputEventDispatcher final : public Runnable
+{
+public:
+  EditorInputEventDispatcher(EditorBase* aEditorBase,
+                             nsIContent* aTarget,
+                             bool aIsComposing)
+    : mEditorBase(aEditorBase)
+    , mTarget(aTarget)
+    , mIsComposing(aIsComposing)
+  {
+  }
+
+  NS_IMETHOD Run() override
+  {
+    // Note that we don't need to check mDispatchInputEvent here.  We need
+    // to check it only when the editor requests to dispatch the input event.
+
+    if (!mTarget->IsInComposedDoc()) {
+      return NS_OK;
+    }
+
+    nsCOMPtr<nsIPresShell> ps = mEditorBase->GetPresShell();
+    if (!ps) {
+      return NS_OK;
+    }
+
+    nsCOMPtr<nsIWidget> widget = mEditorBase->GetWidget();
+    if (!widget) {
+      return NS_OK;
+    }
+
+    // Even if the change is caused by untrusted event, we need to dispatch
+    // trusted input event since it's a fact.
+    InternalEditorInputEvent inputEvent(true, eEditorInput, widget);
+    inputEvent.mTime = static_cast<uint64_t>(PR_Now() / 1000);
+    inputEvent.mIsComposing = mIsComposing;
+    nsEventStatus status = nsEventStatus_eIgnore;
+    nsresult rv =
+      ps->HandleEventWithTarget(&inputEvent, nullptr, mTarget, &status);
+    NS_ENSURE_SUCCESS(rv, NS_OK); // print the warning if error
+    return NS_OK;
+  }
+
+private:
+  RefPtr<EditorBase> mEditorBase;
+  nsCOMPtr<nsIContent> mTarget;
+  bool mIsComposing;
+};
+
+void
+EditorBase::NotifyEditorObservers(NotificationForEditorObservers aNotification)
+{
+  // Copy the observers since EditAction()s can modify mEditorObservers.
+  nsTArray<mozilla::OwningNonNull<nsIEditorObserver>> observers(mEditorObservers);
+  switch (aNotification) {
+    case eNotifyEditorObserversOfEnd:
+      mIsInEditAction = false;
+      for (auto& observer : observers) {
+        observer->EditAction();
+      }
+
+      if (!mDispatchInputEvent) {
+        return;
+      }
+
+      FireInputEvent();
+      break;
+    case eNotifyEditorObserversOfBefore:
+      if (NS_WARN_IF(mIsInEditAction)) {
+        break;
+      }
+      mIsInEditAction = true;
+      for (auto& observer : observers) {
+        observer->BeforeEditAction();
+      }
+      break;
+    case eNotifyEditorObserversOfCancel:
+      mIsInEditAction = false;
+      for (auto& observer : observers) {
+        observer->CancelEditAction();
+      }
+      break;
+    default:
+      MOZ_CRASH("Handle all notifications here");
+      break;
+  }
+}
+
+void
+EditorBase::FireInputEvent()
+{
+  // We don't need to dispatch multiple input events if there is a pending
+  // input event.  However, it may have different event target.  If we resolved
+  // this issue, we need to manage the pending events in an array.  But it's
+  // overwork.  We don't need to do it for the very rare case.
+
+  nsCOMPtr<nsIContent> target = GetInputEventTargetContent();
+  NS_ENSURE_TRUE_VOID(target);
+
+  // NOTE: Don't refer IsIMEComposing() because it returns false even before
+  //       compositionend.  However, DOM Level 3 Events defines it should be
+  //       true after compositionstart and before compositionend.
+  nsContentUtils::AddScriptRunner(
+    new EditorInputEventDispatcher(this, target, !!GetComposition()));
+}
+
+NS_IMETHODIMP
+EditorBase::AddEditActionListener(nsIEditActionListener* aListener)
+{
+  NS_ENSURE_TRUE(aListener, NS_ERROR_NULL_POINTER);
+
+  // Make sure the listener isn't already on the list
+  if (!mActionListeners.Contains(aListener)) {
+    mActionListeners.AppendElement(*aListener);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::RemoveEditActionListener(nsIEditActionListener* aListener)
+{
+  NS_ENSURE_TRUE(aListener, NS_ERROR_FAILURE);
+
+  mActionListeners.RemoveElement(aListener);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::AddDocumentStateListener(nsIDocumentStateListener* aListener)
+{
+  NS_ENSURE_TRUE(aListener, NS_ERROR_NULL_POINTER);
+
+  if (!mDocStateListeners.Contains(aListener)) {
+    mDocStateListeners.AppendElement(*aListener);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::RemoveDocumentStateListener(nsIDocumentStateListener* aListener)
+{
+  NS_ENSURE_TRUE(aListener, NS_ERROR_NULL_POINTER);
+
+  mDocStateListeners.RemoveElement(aListener);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::OutputToString(const nsAString& aFormatType,
+                           uint32_t aFlags,
+                           nsAString& aOutputString)
+{
+  // these should be implemented by derived classes.
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+EditorBase::OutputToStream(nsIOutputStream* aOutputStream,
+                           const nsAString& aFormatType,
+                           const nsACString& aCharsetOverride,
+                           uint32_t aFlags)
+{
+  // these should be implemented by derived classes.
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+EditorBase::DumpContentTree()
+{
+#ifdef DEBUG
+  if (mRootElement) {
+    mRootElement->List(stdout);
+  }
+#endif
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::DebugDumpContent()
+{
+#ifdef DEBUG
+  nsCOMPtr<nsIDOMHTMLDocument> doc = do_QueryReferent(mDocWeak);
+  NS_ENSURE_TRUE(doc, NS_ERROR_NOT_INITIALIZED);
+
+  nsCOMPtr<nsIDOMHTMLElement>bodyElem;
+  doc->GetBody(getter_AddRefs(bodyElem));
+  nsCOMPtr<nsIContent> content = do_QueryInterface(bodyElem);
+  if (content) {
+    content->List();
+  }
+#endif
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::DebugUnitTests(int32_t* outNumTests,
+                           int32_t* outNumTestsFailed)
+{
+#ifdef DEBUG
+  NS_NOTREACHED("This should never get called. Overridden by subclasses");
+#endif
+  return NS_OK;
+}
+
+bool
+EditorBase::ArePreservingSelection()
+{
+  return !(mSavedSel.IsEmpty());
+}
+
+void
+EditorBase::PreserveSelectionAcrossActions(Selection* aSel)
+{
+  mSavedSel.SaveSelection(aSel);
+  mRangeUpdater.RegisterSelectionState(mSavedSel);
+}
+
+nsresult
+EditorBase::RestorePreservedSelection(Selection* aSel)
+{
+  if (mSavedSel.IsEmpty()) {
+    return NS_ERROR_FAILURE;
+  }
+  mSavedSel.RestoreSelection(aSel);
+  StopPreservingSelection();
+  return NS_OK;
+}
+
+void
+EditorBase::StopPreservingSelection()
+{
+  mRangeUpdater.DropSelectionState(mSavedSel);
+  mSavedSel.MakeEmpty();
+}
+
+bool
+EditorBase::EnsureComposition(WidgetCompositionEvent* aCompositionEvent)
+{
+  if (mComposition) {
+    return true;
+  }
+  // The compositionstart event must cause creating new TextComposition
+  // instance at being dispatched by IMEStateManager.
+  mComposition = IMEStateManager::GetTextCompositionFor(aCompositionEvent);
+  if (!mComposition) {
+    // However, TextComposition may be committed before the composition
+    // event comes here.
+    return false;
+  }
+  mComposition->StartHandlingComposition(this);
+  return true;
+}
+
+nsresult
+EditorBase::BeginIMEComposition(WidgetCompositionEvent* aCompositionEvent)
+{
+  MOZ_ASSERT(!mComposition, "There is composition already");
+  if (!EnsureComposition(aCompositionEvent)) {
+    return NS_OK;
+  }
+  if (mPhonetic) {
+    mPhonetic->Truncate(0);
+  }
+  return NS_OK;
+}
+
+void
+EditorBase::EndIMEComposition()
+{
+  NS_ENSURE_TRUE_VOID(mComposition); // nothing to do
+
+  // commit the IME transaction..we can get at it via the transaction mgr.
+  // Note that this means IME won't work without an undo stack!
+  if (mTxnMgr) {
+    nsCOMPtr<nsITransaction> txn = mTxnMgr->PeekUndoStack();
+    nsCOMPtr<nsIAbsorbingTransaction> plcTxn = do_QueryInterface(txn);
+    if (plcTxn) {
+      DebugOnly<nsresult> rv = plcTxn->Commit();
+      NS_ASSERTION(NS_SUCCEEDED(rv),
+                   "nsIAbsorbingTransaction::Commit() failed");
+    }
+  }
+
+  // Composition string may have hidden the caret.  Therefore, we need to
+  // cancel it here.
+  HideCaret(false);
+
+  /* reset the data we need to construct a transaction */
+  mIMETextNode = nullptr;
+  mIMETextOffset = 0;
+  mIMETextLength = 0;
+  mComposition->EndHandlingComposition(this);
+  mComposition = nullptr;
+
+  // notify editor observers of action
+  NotifyEditorObservers(eNotifyEditorObserversOfEnd);
+}
+
+NS_IMETHODIMP
+EditorBase::GetPhonetic(nsAString& aPhonetic)
+{
+  if (mPhonetic) {
+    aPhonetic = *mPhonetic;
+  } else {
+    aPhonetic.Truncate(0);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::ForceCompositionEnd()
+{
+  nsCOMPtr<nsIPresShell> ps = GetPresShell();
+  if (!ps) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+  nsPresContext* pc = ps->GetPresContext();
+  if (!pc) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  return mComposition ?
+    IMEStateManager::NotifyIME(REQUEST_TO_COMMIT_COMPOSITION, pc) : NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::GetPreferredIMEState(IMEState* aState)
+{
+  NS_ENSURE_ARG_POINTER(aState);
+  aState->mEnabled = IMEState::ENABLED;
+  aState->mOpen = IMEState::DONT_CHANGE_OPEN_STATE;
+
+  if (IsReadonly() || IsDisabled()) {
+    aState->mEnabled = IMEState::DISABLED;
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIContent> content = GetRoot();
+  NS_ENSURE_TRUE(content, NS_ERROR_FAILURE);
+
+  nsIFrame* frame = content->GetPrimaryFrame();
+  NS_ENSURE_TRUE(frame, NS_ERROR_FAILURE);
+
+  switch (frame->StyleUIReset()->mIMEMode) {
+    case NS_STYLE_IME_MODE_AUTO:
+      if (IsPasswordEditor())
+        aState->mEnabled = IMEState::PASSWORD;
+      break;
+    case NS_STYLE_IME_MODE_DISABLED:
+      // we should use password state for |ime-mode: disabled;|.
+      aState->mEnabled = IMEState::PASSWORD;
+      break;
+    case NS_STYLE_IME_MODE_ACTIVE:
+      aState->mOpen = IMEState::OPEN;
+      break;
+    case NS_STYLE_IME_MODE_INACTIVE:
+      aState->mOpen = IMEState::CLOSED;
+      break;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::GetComposing(bool* aResult)
+{
+  NS_ENSURE_ARG_POINTER(aResult);
+  *aResult = IsIMEComposing();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::GetRootElement(nsIDOMElement** aRootElement)
+{
+  NS_ENSURE_ARG_POINTER(aRootElement);
+  NS_ENSURE_TRUE(mRootElement, NS_ERROR_NOT_AVAILABLE);
+  nsCOMPtr<nsIDOMElement> rootElement = do_QueryInterface(mRootElement);
+  rootElement.forget(aRootElement);
+  return NS_OK;
+}
+
+/**
+ * All editor operations which alter the doc should be prefaced
+ * with a call to StartOperation, naming the action and direction.
+ */
+NS_IMETHODIMP
+EditorBase::StartOperation(EditAction opID,
+                           nsIEditor::EDirection aDirection)
+{
+  mAction = opID;
+  mDirection = aDirection;
+  return NS_OK;
+}
+
+/**
+ * All editor operations which alter the doc should be followed
+ * with a call to EndOperation.
+ */
+NS_IMETHODIMP
+EditorBase::EndOperation()
+{
+  mAction = EditAction::none;
+  mDirection = eNone;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::CloneAttribute(const nsAString& aAttribute,
+                           nsIDOMNode* aDestNode,
+                           nsIDOMNode* aSourceNode)
+{
+  NS_ENSURE_TRUE(aDestNode && aSourceNode, NS_ERROR_NULL_POINTER);
+
+  nsCOMPtr<nsIDOMElement> destElement = do_QueryInterface(aDestNode);
+  nsCOMPtr<nsIDOMElement> sourceElement = do_QueryInterface(aSourceNode);
+  NS_ENSURE_TRUE(destElement && sourceElement, NS_ERROR_NO_INTERFACE);
+
+  nsAutoString attrValue;
+  bool isAttrSet;
+  nsresult rv = GetAttributeValue(sourceElement,
+                                  aAttribute,
+                                  attrValue,
+                                  &isAttrSet);
+  NS_ENSURE_SUCCESS(rv, rv);
+  if (isAttrSet) {
+    rv = SetAttribute(destElement, aAttribute, attrValue);
+  } else {
+    rv = RemoveAttribute(destElement, aAttribute);
+  }
+
+  return rv;
+}
+
+/**
+ * @param aDest     Must be a DOM element.
+ * @param aSource   Must be a DOM element.
+ */
+NS_IMETHODIMP
+EditorBase::CloneAttributes(nsIDOMNode* aDest,
+                            nsIDOMNode* aSource)
+{
+  NS_ENSURE_TRUE(aDest && aSource, NS_ERROR_NULL_POINTER);
+
+  nsCOMPtr<Element> dest = do_QueryInterface(aDest);
+  nsCOMPtr<Element> source = do_QueryInterface(aSource);
+  NS_ENSURE_TRUE(dest && source, NS_ERROR_NO_INTERFACE);
+
+  CloneAttributes(dest, source);
+
+  return NS_OK;
+}
+
+void
+EditorBase::CloneAttributes(Element* aDest,
+                            Element* aSource)
+{
+  MOZ_ASSERT(aDest && aSource);
+
+  AutoEditBatch beginBatching(this);
+
+  // Use transaction system for undo only if destination is already in the
+  // document
+  NS_ENSURE_TRUE(GetRoot(), );
+  bool destInBody = GetRoot()->Contains(aDest);
+
+  // Clear existing attributes
+  RefPtr<nsDOMAttributeMap> destAttributes = aDest->Attributes();
+  while (RefPtr<Attr> attr = destAttributes->Item(0)) {
+    if (destInBody) {
+      RemoveAttribute(static_cast<nsIDOMElement*>(GetAsDOMNode(aDest)),
+                      attr->NodeName());
+    } else {
+      ErrorResult ignored;
+      aDest->RemoveAttribute(attr->NodeName(), ignored);
+    }
+  }
+
+  // Set just the attributes that the source element has
+  RefPtr<nsDOMAttributeMap> sourceAttributes = aSource->Attributes();
+  uint32_t sourceCount = sourceAttributes->Length();
+  for (uint32_t i = 0; i < sourceCount; i++) {
+    RefPtr<Attr> attr = sourceAttributes->Item(i);
+    nsAutoString value;
+    attr->GetValue(value);
+    if (destInBody) {
+      SetAttributeOrEquivalent(static_cast<nsIDOMElement*>(GetAsDOMNode(aDest)),
+                               attr->NodeName(), value, false);
+    } else {
+      // The element is not inserted in the document yet, we don't want to put
+      // a transaction on the UndoStack
+      SetAttributeOrEquivalent(static_cast<nsIDOMElement*>(GetAsDOMNode(aDest)),
+                               attr->NodeName(), value, true);
+    }
+  }
+}
+
+NS_IMETHODIMP
+EditorBase::ScrollSelectionIntoView(bool aScrollToAnchor)
+{
+  nsCOMPtr<nsISelectionController> selCon;
+  if (NS_SUCCEEDED(GetSelectionController(getter_AddRefs(selCon))) && selCon) {
+    int16_t region = nsISelectionController::SELECTION_FOCUS_REGION;
+
+    if (aScrollToAnchor) {
+      region = nsISelectionController::SELECTION_ANCHOR_REGION;
+    }
+
+    selCon->ScrollSelectionIntoView(nsISelectionController::SELECTION_NORMAL,
+      region, nsISelectionController::SCROLL_OVERFLOW_HIDDEN);
+  }
+
+  return NS_OK;
+}
+
+void
+EditorBase::FindBetterInsertionPoint(nsCOMPtr<nsIDOMNode>& aNode,
+                                     int32_t& aOffset)
+{
+  nsCOMPtr<nsINode> node = do_QueryInterface(aNode);
+  FindBetterInsertionPoint(node, aOffset);
+  aNode = do_QueryInterface(node);
+}
+
+void
+EditorBase::FindBetterInsertionPoint(nsCOMPtr<nsINode>& aNode,
+                                     int32_t& aOffset)
+{
+  if (aNode->IsNodeOfType(nsINode::eTEXT)) {
+    // There is no "better" insertion point.
+    return;
+  }
+
+  if (!IsPlaintextEditor()) {
+    // We cannot find "better" insertion point in HTML editor.
+    // WARNING: When you add some code to find better node in HTML editor,
+    //          you need to call this before calling InsertTextImpl() in
+    //          HTMLEditRules.
+    return;
+  }
+
+  nsCOMPtr<nsINode> node = aNode;
+  int32_t offset = aOffset;
+
+  nsCOMPtr<nsINode> root = GetRoot();
+  if (aNode == root) {
+    // In some cases, aNode is the anonymous DIV, and offset is 0.  To avoid
+    // injecting unneeded text nodes, we first look to see if we have one
+    // available.  In that case, we'll just adjust node and offset accordingly.
+    if (!offset && node->HasChildren() &&
+        node->GetFirstChild()->IsNodeOfType(nsINode::eTEXT)) {
+      aNode = node->GetFirstChild();
+      aOffset = 0;
+      return;
+    }
+
+    // In some other cases, aNode is the anonymous DIV, and offset points to the
+    // terminating mozBR.  In that case, we'll adjust aInOutNode and
+    // aInOutOffset to the preceding text node, if any.
+    if (offset > 0 && node->GetChildAt(offset - 1) &&
+        node->GetChildAt(offset - 1)->IsNodeOfType(nsINode::eTEXT)) {
+      NS_ENSURE_TRUE_VOID(node->Length() <= INT32_MAX);
+      aNode = node->GetChildAt(offset - 1);
+      aOffset = static_cast<int32_t>(aNode->Length());
+      return;
+    }
+  }
+
+  // Sometimes, aNode is the mozBR element itself.  In that case, we'll adjust
+  // the insertion point to the previous text node, if one exists, or to the
+  // parent anonymous DIV.
+  if (TextEditUtils::IsMozBR(node) && !offset) {
+    if (node->GetPreviousSibling() &&
+        node->GetPreviousSibling()->IsNodeOfType(nsINode::eTEXT)) {
+      NS_ENSURE_TRUE_VOID(node->Length() <= INT32_MAX);
+      aNode = node->GetPreviousSibling();
+      aOffset = static_cast<int32_t>(aNode->Length());
+      return;
+    }
+
+    if (node->GetParentNode() && node->GetParentNode() == root) {
+      aNode = node->GetParentNode();
+      aOffset = 0;
+      return;
+    }
+  }
+}
+
+nsresult
+EditorBase::InsertTextImpl(const nsAString& aStringToInsert,
+                           nsCOMPtr<nsINode>* aInOutNode,
+                           int32_t* aInOutOffset,
+                           nsIDocument* aDoc)
+{
+  // NOTE: caller *must* have already used AutoTransactionsConserveSelection
+  // stack-based class to turn off txn selection updating.  Caller also turned
+  // on rules sniffing if desired.
+
+  NS_ENSURE_TRUE(aInOutNode && *aInOutNode && aInOutOffset && aDoc,
+                 NS_ERROR_NULL_POINTER);
+
+  if (!ShouldHandleIMEComposition() && aStringToInsert.IsEmpty()) {
+    return NS_OK;
+  }
+
+  // This method doesn't support over INT32_MAX length text since aInOutOffset
+  // is int32_t*.
+  CheckedInt<int32_t> lengthToInsert(aStringToInsert.Length());
+  NS_ENSURE_TRUE(lengthToInsert.isValid(), NS_ERROR_INVALID_ARG);
+
+  nsCOMPtr<nsINode> node = *aInOutNode;
+  int32_t offset = *aInOutOffset;
+
+  // In some cases, the node may be the anonymous div elemnt or a mozBR
+  // element.  Let's try to look for better insertion point in the nearest
+  // text node if there is.
+  FindBetterInsertionPoint(node, offset);
+
+  if (ShouldHandleIMEComposition()) {
+    CheckedInt<int32_t> newOffset;
+    if (!node->IsNodeOfType(nsINode::eTEXT)) {
+      // create a text node
+      RefPtr<nsTextNode> newNode = aDoc->CreateTextNode(EmptyString());
+      // then we insert it into the dom tree
+      nsresult rv = InsertNode(*newNode, *node, offset);
+      NS_ENSURE_SUCCESS(rv, rv);
+      node = newNode;
+      offset = 0;
+      newOffset = lengthToInsert;
+    } else {
+      newOffset = lengthToInsert + offset;
+      NS_ENSURE_TRUE(newOffset.isValid(), NS_ERROR_FAILURE);
+    }
+    nsresult rv =
+      InsertTextIntoTextNodeImpl(aStringToInsert, *node->GetAsText(), offset);
+    NS_ENSURE_SUCCESS(rv, rv);
+    offset = newOffset.value();
+  } else {
+    if (node->IsNodeOfType(nsINode::eTEXT)) {
+      CheckedInt<int32_t> newOffset = lengthToInsert + offset;
+      NS_ENSURE_TRUE(newOffset.isValid(), NS_ERROR_FAILURE);
+      // we are inserting text into an existing text node.
+      nsresult rv =
+        InsertTextIntoTextNodeImpl(aStringToInsert, *node->GetAsText(), offset);
+      NS_ENSURE_SUCCESS(rv, rv);
+      offset = newOffset.value();
+    } else {
+      // we are inserting text into a non-text node.  first we have to create a
+      // textnode (this also populates it with the text)
+      RefPtr<nsTextNode> newNode = aDoc->CreateTextNode(aStringToInsert);
+      // then we insert it into the dom tree
+      nsresult rv = InsertNode(*newNode, *node, offset);
+      NS_ENSURE_SUCCESS(rv, rv);
+      node = newNode;
+      offset = lengthToInsert.value();
+    }
+  }
+
+  *aInOutNode = node;
+  *aInOutOffset = offset;
+  return NS_OK;
+}
+
+nsresult
+EditorBase::InsertTextIntoTextNodeImpl(const nsAString& aStringToInsert,
+                                       Text& aTextNode,
+                                       int32_t aOffset,
+                                       bool aSuppressIME)
+{
+  RefPtr<EditTransactionBase> transaction;
+  bool isIMETransaction = false;
+  RefPtr<Text> insertedTextNode = &aTextNode;
+  int32_t insertedOffset = aOffset;
+  // aSuppressIME is used when editor must insert text, yet this text is not
+  // part of the current IME operation. Example: adjusting whitespace around an
+  // IME insertion.
+  if (ShouldHandleIMEComposition() && !aSuppressIME) {
+    if (!mIMETextNode) {
+      mIMETextNode = &aTextNode;
+      mIMETextOffset = aOffset;
+    }
+    // Modify mPhonetic with raw text input clauses.
+    const TextRangeArray* ranges = mComposition->GetRanges();
+    for (uint32_t i = 0; i < (ranges ? ranges->Length() : 0); ++i) {
+      const TextRange& textRange = ranges->ElementAt(i);
+      if (!textRange.Length() ||
+          textRange.mRangeType != TextRangeType::eRawClause) {
+        continue;
+      }
+      if (!mPhonetic) {
+        mPhonetic = new nsString();
+      }
+      nsAutoString stringToInsert(aStringToInsert);
+      stringToInsert.Mid(*mPhonetic,
+                         textRange.mStartOffset, textRange.Length());
+    }
+
+    transaction = CreateTxnForComposition(aStringToInsert);
+    isIMETransaction = true;
+    // All characters of the composition string will be replaced with
+    // aStringToInsert.  So, we need to emulate to remove the composition
+    // string.
+    insertedTextNode = mIMETextNode;
+    insertedOffset = mIMETextOffset;
+    mIMETextLength = aStringToInsert.Length();
+  } else {
+    transaction = CreateTxnForInsertText(aStringToInsert, aTextNode, aOffset);
+  }
+
+  // Let listeners know what's up
+  for (auto& listener : mActionListeners) {
+    listener->WillInsertText(
+      static_cast<nsIDOMCharacterData*>(insertedTextNode->AsDOMNode()),
+      insertedOffset, aStringToInsert);
+  }
+
+  // XXX We may not need these view batches anymore.  This is handled at a
+  // higher level now I believe.
+  BeginUpdateViewBatch();
+  nsresult rv = DoTransaction(transaction);
+  EndUpdateViewBatch();
+
+  // let listeners know what happened
+  for (auto& listener : mActionListeners) {
+    listener->DidInsertText(
+      static_cast<nsIDOMCharacterData*>(insertedTextNode->AsDOMNode()),
+      insertedOffset, aStringToInsert, rv);
+  }
+
+  // Added some cruft here for bug 43366.  Layout was crashing because we left
+  // an empty text node lying around in the document.  So I delete empty text
+  // nodes caused by IME.  I have to mark the IME transaction as "fixed", which
+  // means that furure IME txns won't merge with it.  This is because we don't
+  // want future IME txns trying to put their text into a node that is no
+  // longer in the document.  This does not break undo/redo, because all these
+  // txns are wrapped in a parent PlaceHolder txn, and placeholder txns are
+  // already savvy to having multiple ime txns inside them.
+
+  // Delete empty IME text node if there is one
+  if (isIMETransaction && mIMETextNode) {
+    uint32_t len = mIMETextNode->Length();
+    if (!len) {
+      DeleteNode(mIMETextNode);
+      mIMETextNode = nullptr;
+      static_cast<CompositionTransaction*>(transaction.get())->MarkFixed();
+    }
+  }
+
+  return rv;
+}
+
+nsresult
+EditorBase::SelectEntireDocument(Selection* aSelection)
+{
+  if (!aSelection) {
+    return NS_ERROR_NULL_POINTER;
+  }
+
+  nsCOMPtr<nsIDOMElement> rootElement = do_QueryInterface(GetRoot());
+  if (!rootElement) {
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+
+  return aSelection->SelectAllChildren(rootElement);
+}
+
+nsINode*
+EditorBase::GetFirstEditableNode(nsINode* aRoot)
+{
+  MOZ_ASSERT(aRoot);
+
+  nsIContent* node = GetLeftmostChild(aRoot);
+  if (node && !IsEditable(node)) {
+    node = GetNextNode(node, /* aEditableNode = */ true);
+  }
+
+  return (node != aRoot) ? node : nullptr;
+}
+
+NS_IMETHODIMP
+EditorBase::NotifyDocumentListeners(
+              TDocumentListenerNotification aNotificationType)
+{
+  if (!mDocStateListeners.Length()) {
+    // Maybe there just aren't any.
+    return NS_OK;
+  }
+
+  nsTArray<OwningNonNull<nsIDocumentStateListener>>
+    listeners(mDocStateListeners);
+  nsresult rv = NS_OK;
+
+  switch (aNotificationType) {
+    case eDocumentCreated:
+      for (auto& listener : listeners) {
+        rv = listener->NotifyDocumentCreated();
+        if (NS_FAILED(rv)) {
+          break;
+        }
+      }
+      break;
+
+    case eDocumentToBeDestroyed:
+      for (auto& listener : listeners) {
+        rv = listener->NotifyDocumentWillBeDestroyed();
+        if (NS_FAILED(rv)) {
+          break;
+        }
+      }
+      break;
+
+    case eDocumentStateChanged: {
+      bool docIsDirty;
+      rv = GetDocumentModified(&docIsDirty);
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      if (static_cast<int8_t>(docIsDirty) == mDocDirtyState) {
+        return NS_OK;
+      }
+
+      mDocDirtyState = docIsDirty;
+
+      for (auto& listener : listeners) {
+        rv = listener->NotifyDocumentStateChanged(mDocDirtyState);
+        if (NS_FAILED(rv)) {
+          break;
+        }
+      }
+      break;
+    }
+    default:
+      NS_NOTREACHED("Unknown notification");
+  }
+
+  return rv;
+}
+
+already_AddRefed<InsertTextTransaction>
+EditorBase::CreateTxnForInsertText(const nsAString& aStringToInsert,
+                                   Text& aTextNode,
+                                   int32_t aOffset)
+{
+  RefPtr<InsertTextTransaction> transaction =
+    new InsertTextTransaction(aTextNode, aOffset, aStringToInsert, *this,
+                              &mRangeUpdater);
+  return transaction.forget();
+}
+
+nsresult
+EditorBase::DeleteText(nsGenericDOMDataNode& aCharData,
+                       uint32_t aOffset,
+                       uint32_t aLength)
+{
+  RefPtr<DeleteTextTransaction> transaction =
+    CreateTxnForDeleteText(aCharData, aOffset, aLength);
+  NS_ENSURE_STATE(transaction);
+
+  AutoRules beginRulesSniffing(this, EditAction::deleteText,
+                               nsIEditor::ePrevious);
+
+  // Let listeners know what's up
+  for (auto& listener : mActionListeners) {
+    listener->WillDeleteText(
+        static_cast<nsIDOMCharacterData*>(GetAsDOMNode(&aCharData)), aOffset,
+        aLength);
+  }
+
+  nsresult rv = DoTransaction(transaction);
+
+  // Let listeners know what happened
+  for (auto& listener : mActionListeners) {
+    listener->DidDeleteText(
+        static_cast<nsIDOMCharacterData*>(GetAsDOMNode(&aCharData)), aOffset,
+        aLength, rv);
+  }
+
+  return rv;
+}
+
+already_AddRefed<DeleteTextTransaction>
+EditorBase::CreateTxnForDeleteText(nsGenericDOMDataNode& aCharData,
+                                   uint32_t aOffset,
+                                   uint32_t aLength)
+{
+  RefPtr<DeleteTextTransaction> transaction =
+    new DeleteTextTransaction(*this, aCharData, aOffset, aLength,
+                              &mRangeUpdater);
+  nsresult rv = transaction->Init();
+  NS_ENSURE_SUCCESS(rv, nullptr);
+
+  return transaction.forget();
+}
+
+already_AddRefed<SplitNodeTransaction>
+EditorBase::CreateTxnForSplitNode(nsIContent& aNode,
+                                  uint32_t aOffset)
+{
+  RefPtr<SplitNodeTransaction> transaction =
+    new SplitNodeTransaction(*this, aNode, aOffset);
+  return transaction.forget();
+}
+
+already_AddRefed<JoinNodeTransaction>
+EditorBase::CreateTxnForJoinNode(nsINode& aLeftNode,
+                                 nsINode& aRightNode)
+{
+  RefPtr<JoinNodeTransaction> transaction =
+    new JoinNodeTransaction(*this, aLeftNode, aRightNode);
+
+  NS_ENSURE_SUCCESS(transaction->CheckValidity(), nullptr);
+
+  return transaction.forget();
+}
+
+struct SavedRange final
+{
+  RefPtr<Selection> mSelection;
+  nsCOMPtr<nsINode> mStartNode;
+  nsCOMPtr<nsINode> mEndNode;
+  int32_t mStartOffset;
+  int32_t mEndOffset;
+};
+
+nsresult
+EditorBase::SplitNodeImpl(nsIContent& aExistingRightNode,
+                          int32_t aOffset,
+                          nsIContent& aNewLeftNode)
+{
+  // Remember all selection points.
+  AutoTArray<SavedRange, 10> savedRanges;
+  for (size_t i = 0; i < kPresentSelectionTypeCount; ++i) {
+    SelectionType selectionType(ToSelectionType(1 << i));
+    SavedRange range;
+    range.mSelection = GetSelection(selectionType);
+    if (selectionType == SelectionType::eNormal) {
+      NS_ENSURE_TRUE(range.mSelection, NS_ERROR_NULL_POINTER);
+    } else if (!range.mSelection) {
+      // For non-normal selections, skip over the non-existing ones.
+      continue;
+    }
+
+    for (uint32_t j = 0; j < range.mSelection->RangeCount(); ++j) {
+      RefPtr<nsRange> r = range.mSelection->GetRangeAt(j);
+      MOZ_ASSERT(r->IsPositioned());
+      range.mStartNode = r->GetStartParent();
+      range.mStartOffset = r->StartOffset();
+      range.mEndNode = r->GetEndParent();
+      range.mEndOffset = r->EndOffset();
+
+      savedRanges.AppendElement(range);
+    }
+  }
+
+  nsCOMPtr<nsINode> parent = aExistingRightNode.GetParentNode();
+  NS_ENSURE_TRUE(parent, NS_ERROR_NULL_POINTER);
+
+  ErrorResult rv;
+  nsCOMPtr<nsINode> refNode = &aExistingRightNode;
+  parent->InsertBefore(aNewLeftNode, refNode, rv);
+  NS_ENSURE_TRUE(!rv.Failed(), rv.StealNSResult());
+
+  // Split the children between the two nodes.  At this point,
+  // aExistingRightNode has all the children.  Move all the children whose
+  // index is < aOffset to aNewLeftNode.
+  if (aOffset < 0) {
+    // This means move no children
+    return NS_OK;
+  }
+
+  // If it's a text node, just shuffle around some text
+  if (aExistingRightNode.GetAsText() && aNewLeftNode.GetAsText()) {
+    // Fix right node
+    nsAutoString leftText;
+    aExistingRightNode.GetAsText()->SubstringData(0, aOffset, leftText);
+    aExistingRightNode.GetAsText()->DeleteData(0, aOffset);
+    // Fix left node
+    aNewLeftNode.GetAsText()->SetData(leftText);
+  } else {
+    // Otherwise it's an interior node, so shuffle around the children. Go
+    // through list backwards so deletes don't interfere with the iteration.
+    nsCOMPtr<nsINodeList> childNodes = aExistingRightNode.ChildNodes();
+    for (int32_t i = aOffset - 1; i >= 0; i--) {
+      nsCOMPtr<nsIContent> childNode = childNodes->Item(i);
+      if (childNode) {
+        aExistingRightNode.RemoveChild(*childNode, rv);
+        if (!rv.Failed()) {
+          nsCOMPtr<nsIContent> firstChild = aNewLeftNode.GetFirstChild();
+          aNewLeftNode.InsertBefore(*childNode, firstChild, rv);
+        }
+      }
+      if (rv.Failed()) {
+        break;
+      }
+    }
+  }
+
+  // Handle selection
+  nsCOMPtr<nsIPresShell> ps = GetPresShell();
+  if (ps) {
+    ps->FlushPendingNotifications(Flush_Frames);
+  }
+
+  bool shouldSetSelection = GetShouldTxnSetSelection();
+
+  RefPtr<Selection> previousSelection;
+  for (size_t i = 0; i < savedRanges.Length(); ++i) {
+    // Adjust the selection if needed.
+    SavedRange& range = savedRanges[i];
+
+    // If we have not seen the selection yet, clear all of its ranges.
+    if (range.mSelection != previousSelection) {
+      nsresult rv = range.mSelection->RemoveAllRanges();
+      NS_ENSURE_SUCCESS(rv, rv);
+      previousSelection = range.mSelection;
+    }
+
+    if (shouldSetSelection &&
+        range.mSelection->Type() == SelectionType::eNormal) {
+      // If the editor should adjust the selection, don't bother restoring
+      // the ranges for the normal selection here.
+      continue;
+    }
+
+    // Split the selection into existing node and new node.
+    if (range.mStartNode == &aExistingRightNode) {
+      if (range.mStartOffset < aOffset) {
+        range.mStartNode = &aNewLeftNode;
+      } else {
+        range.mStartOffset -= aOffset;
+      }
+    }
+
+    if (range.mEndNode == &aExistingRightNode) {
+      if (range.mEndOffset < aOffset) {
+        range.mEndNode = &aNewLeftNode;
+      } else {
+        range.mEndOffset -= aOffset;
+      }
+    }
+
+    RefPtr<nsRange> newRange;
+    nsresult rv = nsRange::CreateRange(range.mStartNode, range.mStartOffset,
+                                       range.mEndNode, range.mEndOffset,
+                                       getter_AddRefs(newRange));
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = range.mSelection->AddRange(newRange);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  if (shouldSetSelection) {
+    // Editor wants us to set selection at split point.
+    RefPtr<Selection> selection = GetSelection();
+    NS_ENSURE_TRUE(selection, NS_ERROR_NULL_POINTER);
+    selection->Collapse(&aNewLeftNode, aOffset);
+  }
+
+  return NS_OK;
+}
+
+nsresult
+EditorBase::JoinNodesImpl(nsINode* aNodeToKeep,
+                          nsINode* aNodeToJoin,
+                          nsINode* aParent)
+{
+  MOZ_ASSERT(aNodeToKeep);
+  MOZ_ASSERT(aNodeToJoin);
+  MOZ_ASSERT(aParent);
+
+  uint32_t firstNodeLength = aNodeToJoin->Length();
+
+  int32_t joinOffset;
+  GetNodeLocation(aNodeToJoin, &joinOffset);
+  int32_t keepOffset;
+  nsINode* parent = GetNodeLocation(aNodeToKeep, &keepOffset);
+
+  // Remember all selection points.
+  AutoTArray<SavedRange, 10> savedRanges;
+  for (size_t i = 0; i < kPresentSelectionTypeCount; ++i) {
+    SelectionType selectionType(ToSelectionType(1 << i));
+    SavedRange range;
+    range.mSelection = GetSelection(selectionType);
+    if (selectionType == SelectionType::eNormal) {
+      NS_ENSURE_TRUE(range.mSelection, NS_ERROR_NULL_POINTER);
+    } else if (!range.mSelection) {
+      // For non-normal selections, skip over the non-existing ones.
+      continue;
+    }
+
+    for (uint32_t j = 0; j < range.mSelection->RangeCount(); ++j) {
+      RefPtr<nsRange> r = range.mSelection->GetRangeAt(j);
+      MOZ_ASSERT(r->IsPositioned());
+      range.mStartNode = r->GetStartParent();
+      range.mStartOffset = r->StartOffset();
+      range.mEndNode = r->GetEndParent();
+      range.mEndOffset = r->EndOffset();
+
+      // If selection endpoint is between the nodes, remember it as being
+      // in the one that is going away instead.  This simplifies later selection
+      // adjustment logic at end of this method.
+      if (range.mStartNode) {
+        if (range.mStartNode == parent &&
+            joinOffset < range.mStartOffset &&
+            range.mStartOffset <= keepOffset) {
+          range.mStartNode = aNodeToJoin;
+          range.mStartOffset = firstNodeLength;
+        }
+        if (range.mEndNode == parent &&
+            joinOffset < range.mEndOffset &&
+            range.mEndOffset <= keepOffset) {
+          range.mEndNode = aNodeToJoin;
+          range.mEndOffset = firstNodeLength;
+        }
+      }
+
+      savedRanges.AppendElement(range);
+    }
+  }
+
+  // OK, ready to do join now.
+  // If it's a text node, just shuffle around some text.
+  nsCOMPtr<nsIDOMCharacterData> keepNodeAsText( do_QueryInterface(aNodeToKeep) );
+  nsCOMPtr<nsIDOMCharacterData> joinNodeAsText( do_QueryInterface(aNodeToJoin) );
+  if (keepNodeAsText && joinNodeAsText) {
+    nsAutoString rightText;
+    nsAutoString leftText;
+    keepNodeAsText->GetData(rightText);
+    joinNodeAsText->GetData(leftText);
+    leftText += rightText;
+    keepNodeAsText->SetData(leftText);
+  } else {
+    // Otherwise it's an interior node, so shuffle around the children.
+    nsCOMPtr<nsINodeList> childNodes = aNodeToJoin->ChildNodes();
+    MOZ_ASSERT(childNodes);
+
+    // Remember the first child in aNodeToKeep, we'll insert all the children of aNodeToJoin in front of it
+    // GetFirstChild returns nullptr firstNode if aNodeToKeep has no children, that's OK.
+    nsCOMPtr<nsIContent> firstNode = aNodeToKeep->GetFirstChild();
+
+    // Have to go through the list backwards to keep deletes from interfering with iteration.
+    for (uint32_t i = childNodes->Length(); i; --i) {
+      nsCOMPtr<nsIContent> childNode = childNodes->Item(i - 1);
+      if (childNode) {
+        // prepend children of aNodeToJoin
+        ErrorResult err;
+        aNodeToKeep->InsertBefore(*childNode, firstNode, err);
+        NS_ENSURE_TRUE(!err.Failed(), err.StealNSResult());
+        firstNode = childNode.forget();
+      }
+    }
+  }
+
+  // Delete the extra node.
+  ErrorResult err;
+  aParent->RemoveChild(*aNodeToJoin, err);
+
+  bool shouldSetSelection = GetShouldTxnSetSelection();
+
+  RefPtr<Selection> previousSelection;
+  for (size_t i = 0; i < savedRanges.Length(); ++i) {
+    // And adjust the selection if needed.
+    SavedRange& range = savedRanges[i];
+
+    // If we have not seen the selection yet, clear all of its ranges.
+    if (range.mSelection != previousSelection) {
+      nsresult rv = range.mSelection->RemoveAllRanges();
+      NS_ENSURE_SUCCESS(rv, rv);
+      previousSelection = range.mSelection;
+    }
+
+    if (shouldSetSelection &&
+        range.mSelection->Type() == SelectionType::eNormal) {
+      // If the editor should adjust the selection, don't bother restoring
+      // the ranges for the normal selection here.
+      continue;
+    }
+
+    // Check to see if we joined nodes where selection starts.
+    if (range.mStartNode == aNodeToJoin) {
+      range.mStartNode = aNodeToKeep;
+    } else if (range.mStartNode == aNodeToKeep) {
+      range.mStartOffset += firstNodeLength;
+    }
+
+    // Check to see if we joined nodes where selection ends.
+    if (range.mEndNode == aNodeToJoin) {
+      range.mEndNode = aNodeToKeep;
+    } else if (range.mEndNode == aNodeToKeep) {
+      range.mEndOffset += firstNodeLength;
+    }
+
+    RefPtr<nsRange> newRange;
+    nsresult rv = nsRange::CreateRange(range.mStartNode, range.mStartOffset,
+                                       range.mEndNode, range.mEndOffset,
+                                       getter_AddRefs(newRange));
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = range.mSelection->AddRange(newRange);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  if (shouldSetSelection) {
+    // Editor wants us to set selection at join point.
+    RefPtr<Selection> selection = GetSelection();
+    NS_ENSURE_TRUE(selection, NS_ERROR_NULL_POINTER);
+    selection->Collapse(aNodeToKeep, AssertedCast<int32_t>(firstNodeLength));
+  }
+
+  return err.StealNSResult();
+}
+
+int32_t
+EditorBase::GetChildOffset(nsIDOMNode* aChild,
+                           nsIDOMNode* aParent)
+{
+  MOZ_ASSERT(aChild && aParent);
+
+  nsCOMPtr<nsINode> parent = do_QueryInterface(aParent);
+  nsCOMPtr<nsINode> child = do_QueryInterface(aChild);
+  MOZ_ASSERT(parent && child);
+
+  int32_t idx = parent->IndexOf(child);
+  MOZ_ASSERT(idx != -1);
+  return idx;
+}
+
+// static
+already_AddRefed<nsIDOMNode>
+EditorBase::GetNodeLocation(nsIDOMNode* aChild,
+                            int32_t* outOffset)
+{
+  MOZ_ASSERT(aChild && outOffset);
+  NS_ENSURE_TRUE(aChild && outOffset, nullptr);
+  *outOffset = -1;
+
+  nsCOMPtr<nsIDOMNode> parent;
+
+  MOZ_ALWAYS_SUCCEEDS(aChild->GetParentNode(getter_AddRefs(parent)));
+  if (parent) {
+    *outOffset = GetChildOffset(aChild, parent);
+  }
+
+  return parent.forget();
+}
+
+nsINode*
+EditorBase::GetNodeLocation(nsINode* aChild,
+                            int32_t* aOffset)
+{
+  MOZ_ASSERT(aChild);
+  MOZ_ASSERT(aOffset);
+
+  nsINode* parent = aChild->GetParentNode();
+  if (parent) {
+    *aOffset = parent->IndexOf(aChild);
+    MOZ_ASSERT(*aOffset != -1);
+  } else {
+    *aOffset = -1;
+  }
+  return parent;
+}
+
+/**
+ * Returns the number of things inside aNode.  If aNode is text, returns number
+ * of characters. If not, returns number of children nodes.
+ */
+nsresult
+EditorBase::GetLengthOfDOMNode(nsIDOMNode* aNode,
+                               uint32_t& aCount)
+{
+  aCount = 0;
+  nsCOMPtr<nsINode> node = do_QueryInterface(aNode);
+  NS_ENSURE_TRUE(node, NS_ERROR_NULL_POINTER);
+  aCount = node->Length();
+  return NS_OK;
+}
+
+nsIContent*
+EditorBase::GetPriorNode(nsINode* aParentNode,
+                         int32_t aOffset,
+                         bool aEditableNode,
+                         bool aNoBlockCrossing)
+{
+  MOZ_ASSERT(aParentNode);
+
+  // If we are at the beginning of the node, or it is a text node, then just
+  // look before it.
+  if (!aOffset || aParentNode->NodeType() == nsIDOMNode::TEXT_NODE) {
+    if (aNoBlockCrossing && IsBlockNode(aParentNode)) {
+      // If we aren't allowed to cross blocks, don't look before this block.
+      return nullptr;
+    }
+    return GetPriorNode(aParentNode, aEditableNode, aNoBlockCrossing);
+  }
+
+  // else look before the child at 'aOffset'
+  if (nsIContent* child = aParentNode->GetChildAt(aOffset)) {
+    return GetPriorNode(child, aEditableNode, aNoBlockCrossing);
+  }
+
+  // unless there isn't one, in which case we are at the end of the node
+  // and want the deep-right child.
+  nsIContent* resultNode = GetRightmostChild(aParentNode, aNoBlockCrossing);
+  if (!resultNode || !aEditableNode || IsEditable(resultNode)) {
+    return resultNode;
+  }
+
+  // restart the search from the non-editable node we just found
+  return GetPriorNode(resultNode, aEditableNode, aNoBlockCrossing);
+}
+
+nsIContent*
+EditorBase::GetNextNode(nsINode* aParentNode,
+                        int32_t aOffset,
+                        bool aEditableNode,
+                        bool aNoBlockCrossing)
+{
+  MOZ_ASSERT(aParentNode);
+
+  // if aParentNode is a text node, use its location instead
+  if (aParentNode->NodeType() == nsIDOMNode::TEXT_NODE) {
+    nsINode* parent = aParentNode->GetParentNode();
+    NS_ENSURE_TRUE(parent, nullptr);
+    aOffset = parent->IndexOf(aParentNode) + 1; // _after_ the text node
+    aParentNode = parent;
+  }
+
+  // look at the child at 'aOffset'
+  nsIContent* child = aParentNode->GetChildAt(aOffset);
+  if (child) {
+    if (aNoBlockCrossing && IsBlockNode(child)) {
+      return child;
+    }
+
+    nsIContent* resultNode = GetLeftmostChild(child, aNoBlockCrossing);
+    if (!resultNode) {
+      return child;
+    }
+
+    if (!IsDescendantOfEditorRoot(resultNode)) {
+      return nullptr;
+    }
+
+    if (!aEditableNode || IsEditable(resultNode)) {
+      return resultNode;
+    }
+
+    // restart the search from the non-editable node we just found
+    return GetNextNode(resultNode, aEditableNode, aNoBlockCrossing);
+  }
+
+  // unless there isn't one, in which case we are at the end of the node
+  // and want the next one.
+  if (aNoBlockCrossing && IsBlockNode(aParentNode)) {
+    // don't cross out of parent block
+    return nullptr;
+  }
+
+  return GetNextNode(aParentNode, aEditableNode, aNoBlockCrossing);
+}
+
+nsIContent*
+EditorBase::GetPriorNode(nsINode* aCurrentNode,
+                         bool aEditableNode,
+                         bool aNoBlockCrossing /* = false */)
+{
+  MOZ_ASSERT(aCurrentNode);
+
+  if (!IsDescendantOfEditorRoot(aCurrentNode)) {
+    return nullptr;
+  }
+
+  return FindNode(aCurrentNode, false, aEditableNode, aNoBlockCrossing);
+}
+
+nsIContent*
+EditorBase::FindNextLeafNode(nsINode* aCurrentNode,
+                             bool aGoForward,
+                             bool bNoBlockCrossing)
+{
+  // called only by GetPriorNode so we don't need to check params.
+  NS_PRECONDITION(IsDescendantOfEditorRoot(aCurrentNode) &&
+                  !IsEditorRoot(aCurrentNode),
+                  "Bogus arguments");
+
+  nsINode* cur = aCurrentNode;
+  for (;;) {
+    // if aCurrentNode has a sibling in the right direction, return
+    // that sibling's closest child (or itself if it has no children)
+    nsIContent* sibling =
+      aGoForward ? cur->GetNextSibling() : cur->GetPreviousSibling();
+    if (sibling) {
+      if (bNoBlockCrossing && IsBlockNode(sibling)) {
+        // don't look inside prevsib, since it is a block
+        return sibling;
+      }
+      nsIContent *leaf =
+        aGoForward ? GetLeftmostChild(sibling, bNoBlockCrossing) :
+                     GetRightmostChild(sibling, bNoBlockCrossing);
+      if (!leaf) {
+        return sibling;
+      }
+
+      return leaf;
+    }
+
+    nsINode *parent = cur->GetParentNode();
+    if (!parent) {
+      return nullptr;
+    }
+
+    NS_ASSERTION(IsDescendantOfEditorRoot(parent),
+                 "We started with a proper descendant of root, and should stop "
+                 "if we ever hit the root, so we better have a descendant of "
+                 "root now!");
+    if (IsEditorRoot(parent) ||
+        (bNoBlockCrossing && IsBlockNode(parent))) {
+      return nullptr;
+    }
+
+    cur = parent;
+  }
+
+  NS_NOTREACHED("What part of for(;;) do you not understand?");
+  return nullptr;
+}
+
+nsIContent*
+EditorBase::GetNextNode(nsINode* aCurrentNode,
+                        bool aEditableNode,
+                        bool bNoBlockCrossing)
+{
+  MOZ_ASSERT(aCurrentNode);
+
+  if (!IsDescendantOfEditorRoot(aCurrentNode)) {
+    return nullptr;
+  }
+
+  return FindNode(aCurrentNode, true, aEditableNode, bNoBlockCrossing);
+}
+
+nsIContent*
+EditorBase::FindNode(nsINode* aCurrentNode,
+                     bool aGoForward,
+                     bool aEditableNode,
+                     bool bNoBlockCrossing)
+{
+  if (IsEditorRoot(aCurrentNode)) {
+    // Don't allow traversal above the root node! This helps
+    // prevent us from accidentally editing browser content
+    // when the editor is in a text widget.
+
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIContent> candidate =
+    FindNextLeafNode(aCurrentNode, aGoForward, bNoBlockCrossing);
+
+  if (!candidate) {
+    return nullptr;
+  }
+
+  if (!aEditableNode || IsEditable(candidate)) {
+    return candidate;
+  }
+
+  return FindNode(candidate, aGoForward, aEditableNode, bNoBlockCrossing);
+}
+
+nsIContent*
+EditorBase::GetRightmostChild(nsINode* aCurrentNode,
+                              bool bNoBlockCrossing)
+{
+  NS_ENSURE_TRUE(aCurrentNode, nullptr);
+  nsIContent *cur = aCurrentNode->GetLastChild();
+  if (!cur) {
+    return nullptr;
+  }
+  for (;;) {
+    if (bNoBlockCrossing && IsBlockNode(cur)) {
+      return cur;
+    }
+    nsIContent* next = cur->GetLastChild();
+    if (!next) {
+      return cur;
+    }
+    cur = next;
+  }
+
+  NS_NOTREACHED("What part of for(;;) do you not understand?");
+  return nullptr;
+}
+
+nsIContent*
+EditorBase::GetLeftmostChild(nsINode* aCurrentNode,
+                             bool bNoBlockCrossing)
+{
+  NS_ENSURE_TRUE(aCurrentNode, nullptr);
+  nsIContent *cur = aCurrentNode->GetFirstChild();
+  if (!cur) {
+    return nullptr;
+  }
+  for (;;) {
+    if (bNoBlockCrossing && IsBlockNode(cur)) {
+      return cur;
+    }
+    nsIContent *next = cur->GetFirstChild();
+    if (!next) {
+      return cur;
+    }
+    cur = next;
+  }
+
+  NS_NOTREACHED("What part of for(;;) do you not understand?");
+  return nullptr;
+}
+
+bool
+EditorBase::IsBlockNode(nsINode* aNode)
+{
+  // stub to be overridden in HTMLEditor.
+  // screwing around with the class hierarchy here in order
+  // to not duplicate the code in GetNextNode/GetPrevNode
+  // across both EditorBase/HTMLEditor.
+  return false;
+}
+
+bool
+EditorBase::CanContain(nsINode& aParent,
+                       nsIContent& aChild)
+{
+  switch (aParent.NodeType()) {
+    case nsIDOMNode::ELEMENT_NODE:
+    case nsIDOMNode::DOCUMENT_FRAGMENT_NODE:
+      return TagCanContain(*aParent.NodeInfo()->NameAtom(), aChild);
+  }
+  return false;
+}
+
+bool
+EditorBase::CanContainTag(nsINode& aParent,
+                          nsIAtom& aChildTag)
+{
+  switch (aParent.NodeType()) {
+    case nsIDOMNode::ELEMENT_NODE:
+    case nsIDOMNode::DOCUMENT_FRAGMENT_NODE:
+      return TagCanContainTag(*aParent.NodeInfo()->NameAtom(), aChildTag);
+  }
+  return false;
+}
+
+bool
+EditorBase::TagCanContain(nsIAtom& aParentTag,
+                          nsIContent& aChild)
+{
+  switch (aChild.NodeType()) {
+    case nsIDOMNode::TEXT_NODE:
+    case nsIDOMNode::ELEMENT_NODE:
+    case nsIDOMNode::DOCUMENT_FRAGMENT_NODE:
+      return TagCanContainTag(aParentTag, *aChild.NodeInfo()->NameAtom());
+  }
+  return false;
+}
+
+bool
+EditorBase::TagCanContainTag(nsIAtom& aParentTag,
+                             nsIAtom& aChildTag)
+{
+  return true;
+}
+
+bool
+EditorBase::IsRoot(nsIDOMNode* inNode)
+{
+  NS_ENSURE_TRUE(inNode, false);
+
+  nsCOMPtr<nsIDOMNode> rootNode = do_QueryInterface(GetRoot());
+
+  return inNode == rootNode;
+}
+
+bool
+EditorBase::IsRoot(nsINode* inNode)
+{
+  NS_ENSURE_TRUE(inNode, false);
+
+  nsCOMPtr<nsINode> rootNode = GetRoot();
+
+  return inNode == rootNode;
+}
+
+bool
+EditorBase::IsEditorRoot(nsINode* aNode)
+{
+  NS_ENSURE_TRUE(aNode, false);
+  nsCOMPtr<nsINode> rootNode = GetEditorRoot();
+  return aNode == rootNode;
+}
+
+bool
+EditorBase::IsDescendantOfRoot(nsIDOMNode* inNode)
+{
+  nsCOMPtr<nsINode> node = do_QueryInterface(inNode);
+  return IsDescendantOfRoot(node);
+}
+
+bool
+EditorBase::IsDescendantOfRoot(nsINode* inNode)
+{
+  NS_ENSURE_TRUE(inNode, false);
+  nsCOMPtr<nsIContent> root = GetRoot();
+  NS_ENSURE_TRUE(root, false);
+
+  return nsContentUtils::ContentIsDescendantOf(inNode, root);
+}
+
+bool
+EditorBase::IsDescendantOfEditorRoot(nsINode* aNode)
+{
+  NS_ENSURE_TRUE(aNode, false);
+  nsCOMPtr<nsIContent> root = GetEditorRoot();
+  NS_ENSURE_TRUE(root, false);
+
+  return nsContentUtils::ContentIsDescendantOf(aNode, root);
+}
+
+bool
+EditorBase::IsContainer(nsINode* aNode)
+{
+  return aNode ? true : false;
+}
+
+bool
+EditorBase::IsContainer(nsIDOMNode* aNode)
+{
+  return aNode ? true : false;
+}
+
+static inline bool
+IsElementVisible(Element* aElement)
+{
+  if (aElement->GetPrimaryFrame()) {
+    // It's visible, for our purposes
+    return true;
+  }
+
+  nsIContent *cur = aElement;
+  for (;;) {
+    // Walk up the tree looking for the nearest ancestor with a frame.
+    // The state of the child right below it will determine whether
+    // we might possibly have a frame or not.
+    bool haveLazyBitOnChild = cur->HasFlag(NODE_NEEDS_FRAME);
+    cur = cur->GetFlattenedTreeParent();
+    if (!cur) {
+      if (!haveLazyBitOnChild) {
+        // None of our ancestors have lazy bits set, so we shouldn't
+        // have a frame
+        return false;
+      }
+
+      // The root has a lazy frame construction bit.  We need to check
+      // our style.
+      break;
+    }
+
+    if (cur->GetPrimaryFrame()) {
+      if (!haveLazyBitOnChild) {
+        // Our ancestor directly under |cur| doesn't have lazy bits;
+        // that means we won't get a frame
+        return false;
+      }
+
+      if (cur->GetPrimaryFrame()->IsLeaf()) {
+        // Nothing under here will ever get frames
+        return false;
+      }
+
+      // Otherwise, we might end up with a frame when that lazy bit is
+      // processed.  Figure out our actual style.
+      break;
+    }
+  }
+
+  // Now it might be that we have no frame because we're in a
+  // display:none subtree, or it might be that we're just dealing with
+  // lazy frame construction and it hasn't happened yet.  Check which
+  // one it is.
+  RefPtr<nsStyleContext> styleContext =
+    nsComputedDOMStyle::GetStyleContextForElementNoFlush(aElement,
+                                                         nullptr, nullptr);
+  if (styleContext) {
+    return styleContext->StyleDisplay()->mDisplay != StyleDisplay::None;
+  }
+  return false;
+}
+
+bool
+EditorBase::IsEditable(nsIDOMNode* aNode)
+{
+  nsCOMPtr<nsIContent> content = do_QueryInterface(aNode);
+  return IsEditable(content);
+}
+
+bool
+EditorBase::IsEditable(nsINode* aNode)
+{
+  NS_ENSURE_TRUE(aNode, false);
+
+  if (!aNode->IsNodeOfType(nsINode::eCONTENT) || IsMozEditorBogusNode(aNode) ||
+      !IsModifiableNode(aNode)) {
+    return false;
+  }
+
+  // see if it has a frame.  If so, we'll edit it.
+  // special case for textnodes: frame must have width.
+  if (aNode->IsElement() && !IsElementVisible(aNode->AsElement())) {
+    // If the element has no frame, it's not editable.  Note that we
+    // need to check IsElement() here, because some of our tests
+    // rely on frameless textnodes being visible.
+    return false;
+  }
+  switch (aNode->NodeType()) {
+    case nsIDOMNode::ELEMENT_NODE:
+    case nsIDOMNode::TEXT_NODE:
+      return true; // element or text node; not invisible
+    default:
+      return false;
+  }
+}
+
+bool
+EditorBase::IsMozEditorBogusNode(nsINode* element)
+{
+  return element && element->IsElement() &&
+         element->AsElement()->AttrValueIs(kNameSpaceID_None,
+             kMOZEditorBogusNodeAttrAtom, kMOZEditorBogusNodeValue,
+             eCaseMatters);
+}
+
+uint32_t
+EditorBase::CountEditableChildren(nsINode* aNode)
+{
+  MOZ_ASSERT(aNode);
+  uint32_t count = 0;
+  for (nsIContent* child = aNode->GetFirstChild();
+       child;
+       child = child->GetNextSibling()) {
+    if (IsEditable(child)) {
+      ++count;
+    }
+  }
+  return count;
+}
+
+NS_IMETHODIMP
+EditorBase::IncrementModificationCount(int32_t inNumMods)
+{
+  uint32_t oldModCount = mModCount;
+
+  mModCount += inNumMods;
+
+  if ((!oldModCount && mModCount) ||
+      (oldModCount && !mModCount)) {
+    NotifyDocumentListeners(eDocumentStateChanged);
+  }
+  return NS_OK;
+}
+
+
+NS_IMETHODIMP
+EditorBase::GetModificationCount(int32_t* outModCount)
+{
+  NS_ENSURE_ARG_POINTER(outModCount);
+  *outModCount = mModCount;
+  return NS_OK;
+}
+
+
+NS_IMETHODIMP
+EditorBase::ResetModificationCount()
+{
+  bool doNotify = (mModCount != 0);
+
+  mModCount = 0;
+
+  if (doNotify) {
+    NotifyDocumentListeners(eDocumentStateChanged);
+  }
+  return NS_OK;
+}
+
+nsIAtom*
+EditorBase::GetTag(nsIDOMNode* aNode)
+{
+  nsCOMPtr<nsIContent> content = do_QueryInterface(aNode);
+
+  if (!content) {
+    NS_ASSERTION(aNode, "null node passed to EditorBase::GetTag()");
+    return nullptr;
+  }
+
+  return content->NodeInfo()->NameAtom();
+}
+
+nsresult
+EditorBase::GetTagString(nsIDOMNode* aNode,
+                         nsAString& outString)
+{
+  if (!aNode) {
+    NS_NOTREACHED("null node passed to EditorBase::GetTagString()");
+    return NS_ERROR_NULL_POINTER;
+  }
+
+  nsIAtom *atom = GetTag(aNode);
+  if (!atom) {
+    return NS_ERROR_FAILURE;
+  }
+
+  atom->ToString(outString);
+  return NS_OK;
+}
+
+bool
+EditorBase::NodesSameType(nsIDOMNode* aNode1,
+                          nsIDOMNode* aNode2)
+{
+  if (!aNode1 || !aNode2) {
+    NS_NOTREACHED("null node passed to EditorBase::NodesSameType()");
+    return false;
+  }
+
+  nsCOMPtr<nsIContent> content1 = do_QueryInterface(aNode1);
+  NS_ENSURE_TRUE(content1, false);
+
+  nsCOMPtr<nsIContent> content2 = do_QueryInterface(aNode2);
+  NS_ENSURE_TRUE(content2, false);
+
+  return AreNodesSameType(content1, content2);
+}
+
+bool
+EditorBase::AreNodesSameType(nsIContent* aNode1,
+                             nsIContent* aNode2)
+{
+  MOZ_ASSERT(aNode1);
+  MOZ_ASSERT(aNode2);
+  return aNode1->NodeInfo()->NameAtom() == aNode2->NodeInfo()->NameAtom();
+}
+
+bool
+EditorBase::IsTextNode(nsIDOMNode* aNode)
+{
+  if (!aNode) {
+    NS_NOTREACHED("null node passed to IsTextNode()");
+    return false;
+  }
+
+  uint16_t nodeType;
+  aNode->GetNodeType(&nodeType);
+  return (nodeType == nsIDOMNode::TEXT_NODE);
+}
+
+bool
+EditorBase::IsTextNode(nsINode* aNode)
+{
+  return aNode->NodeType() == nsIDOMNode::TEXT_NODE;
+}
+
+nsCOMPtr<nsIDOMNode>
+EditorBase::GetChildAt(nsIDOMNode* aParent, int32_t aOffset)
+{
+  nsCOMPtr<nsIDOMNode> resultNode;
+
+  nsCOMPtr<nsIContent> parent = do_QueryInterface(aParent);
+
+  NS_ENSURE_TRUE(parent, resultNode);
+
+  resultNode = do_QueryInterface(parent->GetChildAt(aOffset));
+
+  return resultNode;
+}
+
+/**
+ * GetNodeAtRangeOffsetPoint() returns the node at this position in a range,
+ * assuming that aParentOrNode is the node itself if it's a text node, or
+ * the node's parent otherwise.
+ */
+nsIContent*
+EditorBase::GetNodeAtRangeOffsetPoint(nsIDOMNode* aParentOrNode,
+                                      int32_t aOffset)
+{
+  nsCOMPtr<nsINode> parentOrNode = do_QueryInterface(aParentOrNode);
+  NS_ENSURE_TRUE(parentOrNode || !aParentOrNode, nullptr);
+  if (parentOrNode->GetAsText()) {
+    return parentOrNode->AsContent();
+  }
+  return parentOrNode->GetChildAt(aOffset);
+}
+
+/**
+ * GetStartNodeAndOffset() returns whatever the start parent & offset is of
+ * the first range in the selection.
+ */
+nsresult
+EditorBase::GetStartNodeAndOffset(Selection* aSelection,
+                                  nsIDOMNode** outStartNode,
+                                  int32_t* outStartOffset)
+{
+  NS_ENSURE_TRUE(outStartNode && outStartOffset && aSelection, NS_ERROR_NULL_POINTER);
+
+  nsCOMPtr<nsINode> startNode;
+  nsresult rv = GetStartNodeAndOffset(aSelection, getter_AddRefs(startNode),
+                                      outStartOffset);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  if (startNode) {
+    NS_ADDREF(*outStartNode = startNode->AsDOMNode());
+  } else {
+    *outStartNode = nullptr;
+  }
+  return NS_OK;
+}
+
+nsresult
+EditorBase::GetStartNodeAndOffset(Selection* aSelection,
+                                  nsINode** aStartNode,
+                                  int32_t* aStartOffset)
+{
+  MOZ_ASSERT(aSelection);
+  MOZ_ASSERT(aStartNode);
+  MOZ_ASSERT(aStartOffset);
+
+  *aStartNode = nullptr;
+  *aStartOffset = 0;
+
+  if (!aSelection->RangeCount()) {
+    return NS_ERROR_FAILURE;
+  }
+
+  const nsRange* range = aSelection->GetRangeAt(0);
+  NS_ENSURE_TRUE(range, NS_ERROR_FAILURE);
+
+  NS_ENSURE_TRUE(range->IsPositioned(), NS_ERROR_FAILURE);
+
+  NS_IF_ADDREF(*aStartNode = range->GetStartParent());
+  *aStartOffset = range->StartOffset();
+  return NS_OK;
+}
+
+/**
+ * GetEndNodeAndOffset() returns whatever the end parent & offset is of
+ * the first range in the selection.
+ */
+nsresult
+EditorBase::GetEndNodeAndOffset(Selection* aSelection,
+                                nsIDOMNode** outEndNode,
+                                int32_t* outEndOffset)
+{
+  NS_ENSURE_TRUE(outEndNode && outEndOffset && aSelection, NS_ERROR_NULL_POINTER);
+
+  nsCOMPtr<nsINode> endNode;
+  nsresult rv = GetEndNodeAndOffset(aSelection, getter_AddRefs(endNode),
+                                    outEndOffset);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (endNode) {
+    NS_ADDREF(*outEndNode = endNode->AsDOMNode());
+  } else {
+    *outEndNode = nullptr;
+  }
+  return NS_OK;
+}
+
+nsresult
+EditorBase::GetEndNodeAndOffset(Selection* aSelection,
+                                nsINode** aEndNode,
+                                int32_t* aEndOffset)
+{
+  MOZ_ASSERT(aSelection);
+  MOZ_ASSERT(aEndNode);
+  MOZ_ASSERT(aEndOffset);
+
+  *aEndNode = nullptr;
+  *aEndOffset = 0;
+
+  NS_ENSURE_TRUE(aSelection->RangeCount(), NS_ERROR_FAILURE);
+
+  const nsRange* range = aSelection->GetRangeAt(0);
+  NS_ENSURE_TRUE(range, NS_ERROR_FAILURE);
+
+  NS_ENSURE_TRUE(range->IsPositioned(), NS_ERROR_FAILURE);
+
+  NS_IF_ADDREF(*aEndNode = range->GetEndParent());
+  *aEndOffset = range->EndOffset();
+  return NS_OK;
+}
+
+/**
+ * IsPreformatted() checks the style info for the node for the preformatted
+ * text style.
+ */
+nsresult
+EditorBase::IsPreformatted(nsIDOMNode* aNode,
+                           bool* aResult)
+{
+  nsCOMPtr<nsIContent> content = do_QueryInterface(aNode);
+
+  NS_ENSURE_TRUE(aResult && content, NS_ERROR_NULL_POINTER);
+
+  nsCOMPtr<nsIPresShell> ps = GetPresShell();
+  NS_ENSURE_TRUE(ps, NS_ERROR_NOT_INITIALIZED);
+
+  // Look at the node (and its parent if it's not an element), and grab its style context
+  RefPtr<nsStyleContext> elementStyle;
+  if (!content->IsElement()) {
+    content = content->GetParent();
+  }
+  if (content && content->IsElement()) {
+    elementStyle = nsComputedDOMStyle::GetStyleContextForElementNoFlush(content->AsElement(),
+                                                                        nullptr,
+                                                                        ps);
+  }
+
+  if (!elementStyle) {
+    // Consider nodes without a style context to be NOT preformatted:
+    // For instance, this is true of JS tags inside the body (which show
+    // up as #text nodes but have no style context).
+    *aResult = false;
+    return NS_OK;
+  }
+
+  const nsStyleText* styleText = elementStyle->StyleText();
+
+  *aResult = styleText->WhiteSpaceIsSignificant();
+  return NS_OK;
+}
+
+
+/**
+ * This splits a node "deeply", splitting children as appropriate.  The place
+ * to split is represented by a DOM point at {splitPointParent,
+ * splitPointOffset}.  That DOM point must be inside aNode, which is the node
+ * to split.  We return the offset in the parent of aNode where the split
+ * terminates - where you would want to insert a new element, for instance, if
+ * that's why you were splitting the node.
+ *
+ * -1 is returned on failure, in unlikely cases like the selection being
+ * unavailable or cloning the node failing.  Make sure not to use the returned
+ * offset for anything without checking that it's valid!  If you're not using
+ * the offset, it's okay to ignore the return value.
+ */
+int32_t
+EditorBase::SplitNodeDeep(nsIContent& aNode,
+                          nsIContent& aSplitPointParent,
+                          int32_t aSplitPointOffset,
+                          EmptyContainers aEmptyContainers,
+                          nsIContent** aOutLeftNode,
+                          nsIContent** aOutRightNode)
+{
+  MOZ_ASSERT(&aSplitPointParent == &aNode ||
+             EditorUtils::IsDescendantOf(&aSplitPointParent, &aNode));
+  int32_t offset = aSplitPointOffset;
+
+  nsCOMPtr<nsIContent> leftNode, rightNode;
+  OwningNonNull<nsIContent> nodeToSplit = aSplitPointParent;
+  while (true) {
+    // Need to insert rules code call here to do things like not split a list
+    // if you are after the last <li> or before the first, etc.  For now we
+    // just have some smarts about unneccessarily splitting text nodes, which
+    // should be universal enough to put straight in this EditorBase routine.
+
+    bool didSplit = false;
+
+    if ((aEmptyContainers == EmptyContainers::yes &&
+         !nodeToSplit->GetAsText()) ||
+        (offset && offset != (int32_t)nodeToSplit->Length())) {
+      didSplit = true;
+      ErrorResult rv;
+      nsCOMPtr<nsIContent> newLeftNode = SplitNode(nodeToSplit, offset, rv);
+      NS_ENSURE_TRUE(!NS_FAILED(rv.StealNSResult()), -1);
+
+      rightNode = nodeToSplit;
+      leftNode = newLeftNode;
+    }
+
+    NS_ENSURE_TRUE(nodeToSplit->GetParent(), -1);
+    OwningNonNull<nsIContent> parentNode = *nodeToSplit->GetParent();
+
+    if (!didSplit && offset) {
+      // Must be "end of text node" case, we didn't split it, just move past it
+      offset = parentNode->IndexOf(nodeToSplit) + 1;
+      leftNode = nodeToSplit;
+    } else {
+      offset = parentNode->IndexOf(nodeToSplit);
+      rightNode = nodeToSplit;
+    }
+
+    if (nodeToSplit == &aNode) {
+      // we split all the way up to (and including) aNode; we're done
+      break;
+    }
+
+    nodeToSplit = parentNode;
+  }
+
+  if (aOutLeftNode) {
+    leftNode.forget(aOutLeftNode);
+  }
+  if (aOutRightNode) {
+    rightNode.forget(aOutRightNode);
+  }
+
+  return offset;
+}
+
+/**
+ * This joins two like nodes "deeply", joining children as appropriate.
+ * Returns the point of the join, or (nullptr, -1) in case of error.
+ */
+EditorDOMPoint
+EditorBase::JoinNodeDeep(nsIContent& aLeftNode,
+                         nsIContent& aRightNode)
+{
+  // While the rightmost children and their descendants of the left node match
+  // the leftmost children and their descendants of the right node, join them
+  // up.
+
+  nsCOMPtr<nsIContent> leftNodeToJoin = &aLeftNode;
+  nsCOMPtr<nsIContent> rightNodeToJoin = &aRightNode;
+  nsCOMPtr<nsINode> parentNode = aRightNode.GetParentNode();
+
+  EditorDOMPoint ret;
+
+  while (leftNodeToJoin && rightNodeToJoin && parentNode &&
+         AreNodesSameType(leftNodeToJoin, rightNodeToJoin)) {
+    uint32_t length = leftNodeToJoin->Length();
+
+    ret.node = rightNodeToJoin;
+    ret.offset = length;
+
+    // Do the join
+    nsresult rv = JoinNodes(*leftNodeToJoin, *rightNodeToJoin);
+    NS_ENSURE_SUCCESS(rv, EditorDOMPoint());
+
+    if (parentNode->GetAsText()) {
+      // We've joined all the way down to text nodes, we're done!
+      return ret;
+    }
+
+    // Get new left and right nodes, and begin anew
+    parentNode = rightNodeToJoin;
+    leftNodeToJoin = parentNode->GetChildAt(length - 1);
+    rightNodeToJoin = parentNode->GetChildAt(length);
+
+    // Skip over non-editable nodes
+    while (leftNodeToJoin && !IsEditable(leftNodeToJoin)) {
+      leftNodeToJoin = leftNodeToJoin->GetPreviousSibling();
+    }
+    if (!leftNodeToJoin) {
+      return ret;
+    }
+
+    while (rightNodeToJoin && !IsEditable(rightNodeToJoin)) {
+      rightNodeToJoin = rightNodeToJoin->GetNextSibling();
+    }
+    if (!rightNodeToJoin) {
+      return ret;
+    }
+  }
+
+  return ret;
+}
+
+void
+EditorBase::BeginUpdateViewBatch()
+{
+  NS_PRECONDITION(mUpdateCount >= 0, "bad state");
+
+  if (!mUpdateCount) {
+    // Turn off selection updates and notifications.
+    RefPtr<Selection> selection = GetSelection();
+    if (selection) {
+      selection->StartBatchChanges();
+    }
+  }
+
+  mUpdateCount++;
+}
+
+nsresult
+EditorBase::EndUpdateViewBatch()
+{
+  NS_PRECONDITION(mUpdateCount > 0, "bad state");
+
+  if (mUpdateCount <= 0) {
+    mUpdateCount = 0;
+    return NS_ERROR_FAILURE;
+  }
+
+  mUpdateCount--;
+
+  if (!mUpdateCount) {
+    // Turn selection updating and notifications back on.
+    RefPtr<Selection> selection = GetSelection();
+    if (selection) {
+      selection->EndBatchChanges();
+    }
+  }
+
+  return NS_OK;
+}
+
+bool
+EditorBase::GetShouldTxnSetSelection()
+{
+  return mShouldTxnSetSelection;
+}
+
+NS_IMETHODIMP
+EditorBase::DeleteSelectionImpl(EDirection aAction,
+                                EStripWrappers aStripWrappers)
+{
+  MOZ_ASSERT(aStripWrappers == eStrip || aStripWrappers == eNoStrip);
+
+  RefPtr<Selection> selection = GetSelection();
+  NS_ENSURE_STATE(selection);
+  RefPtr<EditAggregateTransaction> transaction;
+  nsCOMPtr<nsINode> deleteNode;
+  int32_t deleteCharOffset = 0, deleteCharLength = 0;
+  nsresult rv = CreateTxnForDeleteSelection(aAction,
+                                            getter_AddRefs(transaction),
+                                            getter_AddRefs(deleteNode),
+                                            &deleteCharOffset,
+                                            &deleteCharLength);
+  nsCOMPtr<nsIDOMCharacterData> deleteCharData(do_QueryInterface(deleteNode));
+
+  if (NS_SUCCEEDED(rv)) {
+    AutoRules beginRulesSniffing(this, EditAction::deleteSelection, aAction);
+    // Notify nsIEditActionListener::WillDelete[Selection|Text|Node]
+    if (!deleteNode) {
+      for (auto& listener : mActionListeners) {
+        listener->WillDeleteSelection(selection);
+      }
+    } else if (deleteCharData) {
+      for (auto& listener : mActionListeners) {
+        listener->WillDeleteText(deleteCharData, deleteCharOffset, 1);
+      }
+    } else {
+      for (auto& listener : mActionListeners) {
+        listener->WillDeleteNode(deleteNode->AsDOMNode());
+      }
+    }
+
+    // Delete the specified amount
+    rv = DoTransaction(transaction);
+
+    // Notify nsIEditActionListener::DidDelete[Selection|Text|Node]
+    if (!deleteNode) {
+      for (auto& listener : mActionListeners) {
+        listener->DidDeleteSelection(selection);
+      }
+    } else if (deleteCharData) {
+      for (auto& listener : mActionListeners) {
+        listener->DidDeleteText(deleteCharData, deleteCharOffset, 1, rv);
+      }
+    } else {
+      for (auto& listener : mActionListeners) {
+        listener->DidDeleteNode(deleteNode->AsDOMNode(), rv);
+      }
+    }
+  }
+
+  return rv;
+}
+
+already_AddRefed<Element>
+EditorBase::DeleteSelectionAndCreateElement(nsIAtom& aTag)
+{
+  nsresult rv = DeleteSelectionAndPrepareToCreateNode();
+  NS_ENSURE_SUCCESS(rv, nullptr);
+
+  RefPtr<Selection> selection = GetSelection();
+  NS_ENSURE_TRUE(selection, nullptr);
+
+  nsCOMPtr<nsINode> node = selection->GetAnchorNode();
+  uint32_t offset = selection->AnchorOffset();
+
+  nsCOMPtr<Element> newElement = CreateNode(&aTag, node, offset);
+
+  // We want the selection to be just after the new node
+  rv = selection->Collapse(node, offset + 1);
+  NS_ENSURE_SUCCESS(rv, nullptr);
+
+  return newElement.forget();
+}
+
+TextComposition*
+EditorBase::GetComposition() const
+{
+  return mComposition;
+}
+
+bool
+EditorBase::IsIMEComposing() const
+{
+  return mComposition && mComposition->IsComposing();
+}
+
+bool
+EditorBase::ShouldHandleIMEComposition() const
+{
+  // When the editor is being reframed, the old value may be restored with
+  // InsertText().  In this time, the text should be inserted as not a part
+  // of the composition.
+  return mComposition && mDidPostCreate;
+}
+
+nsresult
+EditorBase::DeleteSelectionAndPrepareToCreateNode()
+{
+  RefPtr<Selection> selection = GetSelection();
+  NS_ENSURE_TRUE(selection, NS_ERROR_NULL_POINTER);
+  MOZ_ASSERT(selection->GetAnchorFocusRange());
+
+  if (!selection->GetAnchorFocusRange()->Collapsed()) {
+    nsresult rv = DeleteSelection(nsIEditor::eNone, nsIEditor::eStrip);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    MOZ_ASSERT(selection->GetAnchorFocusRange() &&
+               selection->GetAnchorFocusRange()->Collapsed(),
+               "Selection not collapsed after delete");
+  }
+
+  // If the selection is a chardata node, split it if necessary and compute
+  // where to put the new node
+  nsCOMPtr<nsINode> node = selection->GetAnchorNode();
+  MOZ_ASSERT(node, "Selection has no ranges in it");
+
+  if (node && node->IsNodeOfType(nsINode::eDATA_NODE)) {
+    NS_ASSERTION(node->GetParentNode(),
+                 "It's impossible to insert into chardata with no parent -- "
+                 "fix the caller");
+    NS_ENSURE_STATE(node->GetParentNode());
+
+    uint32_t offset = selection->AnchorOffset();
+
+    if (!offset) {
+      nsresult rv = selection->Collapse(node->GetParentNode(),
+                                        node->GetParentNode()->IndexOf(node));
+      MOZ_ASSERT(NS_SUCCEEDED(rv));
+      NS_ENSURE_SUCCESS(rv, rv);
+    } else if (offset == node->Length()) {
+      nsresult rv =
+        selection->Collapse(node->GetParentNode(),
+                            node->GetParentNode()->IndexOf(node) + 1);
+      MOZ_ASSERT(NS_SUCCEEDED(rv));
+      NS_ENSURE_SUCCESS(rv, rv);
+    } else {
+      nsCOMPtr<nsIDOMNode> tmp;
+      nsresult rv = SplitNode(node->AsDOMNode(), offset, getter_AddRefs(tmp));
+      NS_ENSURE_SUCCESS(rv, rv);
+      rv = selection->Collapse(node->GetParentNode(),
+                               node->GetParentNode()->IndexOf(node));
+      MOZ_ASSERT(NS_SUCCEEDED(rv));
+      NS_ENSURE_SUCCESS(rv, rv);
+    }
+  }
+  return NS_OK;
+}
+
+void
+EditorBase::DoAfterDoTransaction(nsITransaction* aTxn)
+{
+  bool isTransientTransaction;
+  MOZ_ALWAYS_SUCCEEDS(aTxn->GetIsTransient(&isTransientTransaction));
+
+  if (!isTransientTransaction) {
+    // we need to deal here with the case where the user saved after some
+    // edits, then undid one or more times. Then, the undo count is -ve,
+    // but we can't let a do take it back to zero. So we flip it up to
+    // a +ve number.
+    int32_t modCount;
+    GetModificationCount(&modCount);
+    if (modCount < 0) {
+      modCount = -modCount;
+    }
+
+    // don't count transient transactions
+    MOZ_ALWAYS_SUCCEEDS(IncrementModificationCount(1));
+  }
+}
+
+void
+EditorBase::DoAfterUndoTransaction()
+{
+  // all undoable transactions are non-transient
+  MOZ_ALWAYS_SUCCEEDS(IncrementModificationCount(-1));
+}
+
+void
+EditorBase::DoAfterRedoTransaction()
+{
+  // all redoable transactions are non-transient
+  MOZ_ALWAYS_SUCCEEDS(IncrementModificationCount(1));
+}
+
+already_AddRefed<ChangeAttributeTransaction>
+EditorBase::CreateTxnForSetAttribute(Element& aElement,
+                                     nsIAtom& aAttribute,
+                                     const nsAString& aValue)
+{
+  RefPtr<ChangeAttributeTransaction> transaction =
+    new ChangeAttributeTransaction(aElement, aAttribute, &aValue);
+
+  return transaction.forget();
+}
+
+already_AddRefed<ChangeAttributeTransaction>
+EditorBase::CreateTxnForRemoveAttribute(Element& aElement,
+                                        nsIAtom& aAttribute)
+{
+  RefPtr<ChangeAttributeTransaction> transaction =
+    new ChangeAttributeTransaction(aElement, aAttribute, nullptr);
+
+  return transaction.forget();
+}
+
+already_AddRefed<CreateElementTransaction>
+EditorBase::CreateTxnForCreateElement(nsIAtom& aTag,
+                                      nsINode& aParent,
+                                      int32_t aPosition)
+{
+  RefPtr<CreateElementTransaction> transaction =
+    new CreateElementTransaction(*this, aTag, aParent, aPosition);
+
+  return transaction.forget();
+}
+
+
+already_AddRefed<InsertNodeTransaction>
+EditorBase::CreateTxnForInsertNode(nsIContent& aNode,
+                                   nsINode& aParent,
+                                   int32_t aPosition)
+{
+  RefPtr<InsertNodeTransaction> transaction =
+    new InsertNodeTransaction(aNode, aParent, aPosition, *this);
+  return transaction.forget();
+}
+
+nsresult
+EditorBase::CreateTxnForDeleteNode(nsINode* aNode,
+                                   DeleteNodeTransaction** aTransaction)
+{
+  NS_ENSURE_TRUE(aNode, NS_ERROR_NULL_POINTER);
+
+  RefPtr<DeleteNodeTransaction> transaction = new DeleteNodeTransaction();
+
+  nsresult rv = transaction->Init(this, aNode, &mRangeUpdater);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  transaction.forget(aTransaction);
+  return NS_OK;
+}
+
+already_AddRefed<CompositionTransaction>
+EditorBase::CreateTxnForComposition(const nsAString& aStringToInsert)
+{
+  MOZ_ASSERT(mIMETextNode);
+  // During handling IME composition, mComposition must have been initialized.
+  // TODO: We can simplify CompositionTransaction::Init() with TextComposition
+  //       class.
+  RefPtr<CompositionTransaction> transaction =
+    new CompositionTransaction(*mIMETextNode, mIMETextOffset, mIMETextLength,
+                               mComposition->GetRanges(), aStringToInsert,
+                               *this, &mRangeUpdater);
+  return transaction.forget();
+}
+
+NS_IMETHODIMP
+EditorBase::CreateTxnForAddStyleSheet(StyleSheet* aSheet,
+                                      AddStyleSheetTransaction** aTransaction)
+{
+  RefPtr<AddStyleSheetTransaction> transaction = new AddStyleSheetTransaction();
+
+  nsresult rv = transaction->Init(this, aSheet);
+  if (NS_SUCCEEDED(rv)) {
+    transaction.forget(aTransaction);
+  }
+
+  return rv;
+}
+
+NS_IMETHODIMP
+EditorBase::CreateTxnForRemoveStyleSheet(
+              StyleSheet* aSheet,
+              RemoveStyleSheetTransaction** aTransaction)
+{
+  RefPtr<RemoveStyleSheetTransaction> transaction =
+    new RemoveStyleSheetTransaction();
+
+  nsresult rv = transaction->Init(this, aSheet);
+  if (NS_SUCCEEDED(rv)) {
+    transaction.forget(aTransaction);
+  }
+
+  return rv;
+}
+
+nsresult
+EditorBase::CreateTxnForDeleteSelection(EDirection aAction,
+                                        EditAggregateTransaction** aTransaction,
+                                        nsINode** aNode,
+                                        int32_t* aOffset,
+                                        int32_t* aLength)
+{
+  MOZ_ASSERT(aTransaction);
+  *aTransaction = nullptr;
+
+  RefPtr<Selection> selection = GetSelection();
+  NS_ENSURE_STATE(selection);
+
+  // Check whether the selection is collapsed and we should do nothing:
+  if (selection->Collapsed() && aAction == eNone) {
+    return NS_OK;
+  }
+
+  // allocate the out-param transaction
+  RefPtr<EditAggregateTransaction> aggregateTransaction =
+    new EditAggregateTransaction();
+
+  for (uint32_t rangeIdx = 0; rangeIdx < selection->RangeCount(); ++rangeIdx) {
+    RefPtr<nsRange> range = selection->GetRangeAt(rangeIdx);
+    NS_ENSURE_STATE(range);
+
+    // Same with range as with selection; if it is collapsed and action
+    // is eNone, do nothing.
+    if (!range->Collapsed()) {
+      RefPtr<DeleteRangeTransaction> transaction = new DeleteRangeTransaction();
+      transaction->Init(this, range, &mRangeUpdater);
+      aggregateTransaction->AppendChild(transaction);
+    } else if (aAction != eNone) {
+      // we have an insertion point.  delete the thing in front of it or
+      // behind it, depending on aAction
+      nsresult rv = CreateTxnForDeleteInsertionPoint(range, aAction,
+                                                     aggregateTransaction,
+                                                     aNode, aOffset, aLength);
+      NS_ENSURE_SUCCESS(rv, rv);
+    }
+  }
+
+  aggregateTransaction.forget(aTransaction);
+
+  return NS_OK;
+}
+
+already_AddRefed<DeleteTextTransaction>
+EditorBase::CreateTxnForDeleteCharacter(nsGenericDOMDataNode& aData,
+                                        uint32_t aOffset,
+                                        EDirection aDirection)
+{
+  NS_ASSERTION(aDirection == eNext || aDirection == ePrevious,
+               "Invalid direction");
+  nsAutoString data;
+  aData.GetData(data);
+  NS_ASSERTION(data.Length(), "Trying to delete from a zero-length node");
+  NS_ENSURE_TRUE(data.Length(), nullptr);
+
+  uint32_t segOffset = aOffset, segLength = 1;
+  if (aDirection == eNext) {
+    if (segOffset + 1 < data.Length() &&
+        NS_IS_HIGH_SURROGATE(data[segOffset]) &&
+        NS_IS_LOW_SURROGATE(data[segOffset+1])) {
+      // Delete both halves of the surrogate pair
+      ++segLength;
+    }
+  } else if (aOffset > 0) {
+    --segOffset;
+    if (segOffset > 0 &&
+      NS_IS_LOW_SURROGATE(data[segOffset]) &&
+      NS_IS_HIGH_SURROGATE(data[segOffset-1])) {
+      ++segLength;
+      --segOffset;
+    }
+  } else {
+    return nullptr;
+  }
+  return CreateTxnForDeleteText(aData, segOffset, segLength);
+}
+
+//XXX: currently, this doesn't handle edge conditions because GetNext/GetPrior
+//are not implemented
+nsresult
+EditorBase::CreateTxnForDeleteInsertionPoint(
+              nsRange* aRange,
+              EDirection aAction,
+              EditAggregateTransaction* aTransaction,
+              nsINode** aNode,
+              int32_t* aOffset,
+              int32_t* aLength)
+{
+  MOZ_ASSERT(aAction != eNone);
+
+  // get the node and offset of the insertion point
+  nsCOMPtr<nsINode> node = aRange->GetStartParent();
+  NS_ENSURE_STATE(node);
+
+  int32_t offset = aRange->StartOffset();
+
+  // determine if the insertion point is at the beginning, middle, or end of
+  // the node
+
+  uint32_t count = node->Length();
+
+  bool isFirst = !offset;
+  bool isLast  = (count == (uint32_t)offset);
+
+  // XXX: if isFirst && isLast, then we'll need to delete the node
+  //      as well as the 1 child
+
+  // build a transaction for deleting the appropriate data
+  // XXX: this has to come from rule section
+  if (aAction == ePrevious && isFirst) {
+    // we're backspacing from the beginning of the node.  Delete the first
+    // thing to our left
+    nsCOMPtr<nsIContent> priorNode = GetPriorNode(node, true);
+    NS_ENSURE_STATE(priorNode);
+
+    // there is a priorNode, so delete its last child (if chardata, delete the
+    // last char). if it has no children, delete it
+    if (priorNode->IsNodeOfType(nsINode::eDATA_NODE)) {
+      RefPtr<nsGenericDOMDataNode> priorNodeAsCharData =
+        static_cast<nsGenericDOMDataNode*>(priorNode.get());
+      uint32_t length = priorNode->Length();
+      // Bail out for empty chardata XXX: Do we want to do something else?
+      NS_ENSURE_STATE(length);
+      RefPtr<DeleteTextTransaction> transaction =
+        CreateTxnForDeleteCharacter(*priorNodeAsCharData, length, ePrevious);
+      NS_ENSURE_STATE(transaction);
+
+      *aOffset = transaction->GetOffset();
+      *aLength = transaction->GetNumCharsToDelete();
+      aTransaction->AppendChild(transaction);
+    } else {
+      // priorNode is not chardata, so tell its parent to delete it
+      RefPtr<DeleteNodeTransaction> transaction;
+      nsresult rv =
+        CreateTxnForDeleteNode(priorNode, getter_AddRefs(transaction));
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      aTransaction->AppendChild(transaction);
+    }
+
+    NS_ADDREF(*aNode = priorNode);
+
+    return NS_OK;
+  }
+
+  if (aAction == eNext && isLast) {
+    // we're deleting from the end of the node.  Delete the first thing to our
+    // right
+    nsCOMPtr<nsIContent> nextNode = GetNextNode(node, true);
+    NS_ENSURE_STATE(nextNode);
+
+    // there is a nextNode, so delete its first child (if chardata, delete the
+    // first char). if it has no children, delete it
+    if (nextNode->IsNodeOfType(nsINode::eDATA_NODE)) {
+      RefPtr<nsGenericDOMDataNode> nextNodeAsCharData =
+        static_cast<nsGenericDOMDataNode*>(nextNode.get());
+      uint32_t length = nextNode->Length();
+      // Bail out for empty chardata XXX: Do we want to do something else?
+      NS_ENSURE_STATE(length);
+      RefPtr<DeleteTextTransaction> transaction =
+        CreateTxnForDeleteCharacter(*nextNodeAsCharData, 0, eNext);
+      NS_ENSURE_STATE(transaction);
+
+      *aOffset = transaction->GetOffset();
+      *aLength = transaction->GetNumCharsToDelete();
+      aTransaction->AppendChild(transaction);
+    } else {
+      // nextNode is not chardata, so tell its parent to delete it
+      RefPtr<DeleteNodeTransaction> transaction;
+      nsresult rv =
+        CreateTxnForDeleteNode(nextNode, getter_AddRefs(transaction));
+      NS_ENSURE_SUCCESS(rv, rv);
+      aTransaction->AppendChild(transaction);
+    }
+
+    NS_ADDREF(*aNode = nextNode);
+
+    return NS_OK;
+  }
+
+  if (node->IsNodeOfType(nsINode::eDATA_NODE)) {
+    RefPtr<nsGenericDOMDataNode> nodeAsCharData =
+      static_cast<nsGenericDOMDataNode*>(node.get());
+    // we have chardata, so delete a char at the proper offset
+    RefPtr<DeleteTextTransaction> transaction =
+      CreateTxnForDeleteCharacter(*nodeAsCharData, offset, aAction);
+    NS_ENSURE_STATE(transaction);
+
+    aTransaction->AppendChild(transaction);
+    NS_ADDREF(*aNode = node);
+    *aOffset = transaction->GetOffset();
+    *aLength = transaction->GetNumCharsToDelete();
+  } else {
+    // we're either deleting a node or chardata, need to dig into the next/prev
+    // node to find out
+    nsCOMPtr<nsINode> selectedNode;
+    if (aAction == ePrevious) {
+      selectedNode = GetPriorNode(node, offset, true);
+    } else if (aAction == eNext) {
+      selectedNode = GetNextNode(node, offset, true);
+    }
+
+    while (selectedNode &&
+           selectedNode->IsNodeOfType(nsINode::eDATA_NODE) &&
+           !selectedNode->Length()) {
+      // Can't delete an empty chardata node (bug 762183)
+      if (aAction == ePrevious) {
+        selectedNode = GetPriorNode(selectedNode, true);
+      } else if (aAction == eNext) {
+        selectedNode = GetNextNode(selectedNode, true);
+      }
+    }
+    NS_ENSURE_STATE(selectedNode);
+
+    if (selectedNode->IsNodeOfType(nsINode::eDATA_NODE)) {
+      RefPtr<nsGenericDOMDataNode> selectedNodeAsCharData =
+        static_cast<nsGenericDOMDataNode*>(selectedNode.get());
+      // we are deleting from a chardata node, so do a character deletion
+      uint32_t position = 0;
+      if (aAction == ePrevious) {
+        position = selectedNode->Length();
+      }
+      RefPtr<DeleteTextTransaction> deleteTextTransaction =
+        CreateTxnForDeleteCharacter(*selectedNodeAsCharData, position,
+                                    aAction);
+      NS_ENSURE_TRUE(deleteTextTransaction, NS_ERROR_NULL_POINTER);
+
+      aTransaction->AppendChild(deleteTextTransaction);
+      *aOffset = deleteTextTransaction->GetOffset();
+      *aLength = deleteTextTransaction->GetNumCharsToDelete();
+    } else {
+      RefPtr<DeleteNodeTransaction> deleteNodeTransaction;
+      nsresult rv =
+        CreateTxnForDeleteNode(selectedNode,
+                               getter_AddRefs(deleteNodeTransaction));
+      NS_ENSURE_SUCCESS(rv, rv);
+      NS_ENSURE_TRUE(deleteNodeTransaction, NS_ERROR_NULL_POINTER);
+
+      aTransaction->AppendChild(deleteNodeTransaction);
+    }
+
+    NS_ADDREF(*aNode = selectedNode);
+  }
+
+  return NS_OK;
+}
+
+nsresult
+EditorBase::CreateRange(nsIDOMNode* aStartParent,
+                        int32_t aStartOffset,
+                        nsIDOMNode* aEndParent,
+                        int32_t aEndOffset,
+                        nsRange** aRange)
+{
+  return nsRange::CreateRange(aStartParent, aStartOffset, aEndParent,
+                              aEndOffset, aRange);
+}
+
+nsresult
+EditorBase::AppendNodeToSelectionAsRange(nsIDOMNode* aNode)
+{
+  NS_ENSURE_TRUE(aNode, NS_ERROR_NULL_POINTER);
+  RefPtr<Selection> selection = GetSelection();
+  NS_ENSURE_TRUE(selection, NS_ERROR_FAILURE);
+
+  nsCOMPtr<nsIDOMNode> parentNode;
+  nsresult rv = aNode->GetParentNode(getter_AddRefs(parentNode));
+  NS_ENSURE_SUCCESS(rv, rv);
+  NS_ENSURE_TRUE(parentNode, NS_ERROR_NULL_POINTER);
+
+  int32_t offset = GetChildOffset(aNode, parentNode);
+
+  RefPtr<nsRange> range;
+  rv = CreateRange(parentNode, offset, parentNode, offset + 1,
+                   getter_AddRefs(range));
+  NS_ENSURE_SUCCESS(rv, rv);
+  NS_ENSURE_TRUE(range, NS_ERROR_NULL_POINTER);
+
+  return selection->AddRange(range);
+}
+
+nsresult
+EditorBase::ClearSelection()
+{
+  RefPtr<Selection> selection = GetSelection();
+  NS_ENSURE_TRUE(selection, NS_ERROR_FAILURE);
+  return selection->RemoveAllRanges();
+}
+
+already_AddRefed<Element>
+EditorBase::CreateHTMLContent(nsIAtom* aTag)
+{
+  MOZ_ASSERT(aTag);
+
+  nsCOMPtr<nsIDocument> doc = GetDocument();
+  if (!doc) {
+    return nullptr;
+  }
+
+  // XXX Wallpaper over editor bug (editor tries to create elements with an
+  //     empty nodename).
+  if (aTag == nsGkAtoms::_empty) {
+    NS_ERROR("Don't pass an empty tag to EditorBase::CreateHTMLContent, "
+             "check caller.");
+    return nullptr;
+  }
+
+  return doc->CreateElem(nsDependentAtomString(aTag), nullptr,
+                         kNameSpaceID_XHTML);
+}
+
+nsresult
+EditorBase::SetAttributeOrEquivalent(nsIDOMElement* aElement,
+                                     const nsAString& aAttribute,
+                                     const nsAString& aValue,
+                                     bool aSuppressTransaction)
+{
+  return SetAttribute(aElement, aAttribute, aValue);
+}
+
+nsresult
+EditorBase::RemoveAttributeOrEquivalent(nsIDOMElement* aElement,
+                                        const nsAString& aAttribute,
+                                        bool aSuppressTransaction)
+{
+  return RemoveAttribute(aElement, aAttribute);
+}
+
+nsresult
+EditorBase::HandleKeyPressEvent(nsIDOMKeyEvent* aKeyEvent)
+{
+  // NOTE: When you change this method, you should also change:
+  //   * editor/libeditor/tests/test_texteditor_keyevent_handling.html
+  //   * editor/libeditor/tests/test_htmleditor_keyevent_handling.html
+  //
+  // And also when you add new key handling, you need to change the subclass's
+  // HandleKeyPressEvent()'s switch statement.
+
+  WidgetKeyboardEvent* nativeKeyEvent =
+    aKeyEvent->AsEvent()->WidgetEventPtr()->AsKeyboardEvent();
+  NS_ENSURE_TRUE(nativeKeyEvent, NS_ERROR_UNEXPECTED);
+  NS_ASSERTION(nativeKeyEvent->mMessage == eKeyPress,
+               "HandleKeyPressEvent gets non-keypress event");
+
+  // if we are readonly or disabled, then do nothing.
+  if (IsReadonly() || IsDisabled()) {
+    // consume backspace for disabled and readonly textfields, to prevent
+    // back in history, which could be confusing to users
+    if (nativeKeyEvent->mKeyCode == NS_VK_BACK) {
+      aKeyEvent->AsEvent()->PreventDefault();
+    }
+    return NS_OK;
+  }
+
+  switch (nativeKeyEvent->mKeyCode) {
+    case NS_VK_META:
+    case NS_VK_WIN:
+    case NS_VK_SHIFT:
+    case NS_VK_CONTROL:
+    case NS_VK_ALT:
+      aKeyEvent->AsEvent()->PreventDefault(); // consumed
+      return NS_OK;
+    case NS_VK_BACK:
+      if (nativeKeyEvent->IsControl() || nativeKeyEvent->IsAlt() ||
+          nativeKeyEvent->IsMeta() || nativeKeyEvent->IsOS()) {
+        return NS_OK;
+      }
+      DeleteSelection(nsIEditor::ePrevious, nsIEditor::eStrip);
+      aKeyEvent->AsEvent()->PreventDefault(); // consumed
+      return NS_OK;
+    case NS_VK_DELETE:
+      // on certain platforms (such as windows) the shift key
+      // modifies what delete does (cmd_cut in this case).
+      // bailing here to allow the keybindings to do the cut.
+      if (nativeKeyEvent->IsShift() || nativeKeyEvent->IsControl() ||
+          nativeKeyEvent->IsAlt() || nativeKeyEvent->IsMeta() ||
+          nativeKeyEvent->IsOS()) {
+        return NS_OK;
+      }
+      DeleteSelection(nsIEditor::eNext, nsIEditor::eStrip);
+      aKeyEvent->AsEvent()->PreventDefault(); // consumed
+      return NS_OK;
+  }
+  return NS_OK;
+}
+
+nsresult
+EditorBase::HandleInlineSpellCheck(EditAction action,
+                                   Selection* aSelection,
+                                   nsIDOMNode* previousSelectedNode,
+                                   int32_t previousSelectedOffset,
+                                   nsIDOMNode* aStartNode,
+                                   int32_t aStartOffset,
+                                   nsIDOMNode* aEndNode,
+                                   int32_t aEndOffset)
+{
+  // Have to cast action here because this method is from an IDL
+  return mInlineSpellChecker ? mInlineSpellChecker->SpellCheckAfterEditorChange(
+                                 (int32_t)action, aSelection,
+                                 previousSelectedNode, previousSelectedOffset,
+                                 aStartNode, aStartOffset, aEndNode,
+                                 aEndOffset)
+                             : NS_OK;
+}
+
+already_AddRefed<nsIContent>
+EditorBase::FindSelectionRoot(nsINode* aNode)
+{
+  nsCOMPtr<nsIContent> rootContent = GetRoot();
+  return rootContent.forget();
+}
+
+nsresult
+EditorBase::InitializeSelection(nsIDOMEventTarget* aFocusEventTarget)
+{
+  nsCOMPtr<nsINode> targetNode = do_QueryInterface(aFocusEventTarget);
+  NS_ENSURE_TRUE(targetNode, NS_ERROR_INVALID_ARG);
+  nsCOMPtr<nsIContent> selectionRootContent = FindSelectionRoot(targetNode);
+  if (!selectionRootContent) {
+    return NS_OK;
+  }
+
+  bool isTargetDoc =
+    targetNode->NodeType() == nsIDOMNode::DOCUMENT_NODE &&
+    targetNode->HasFlag(NODE_IS_EDITABLE);
+
+  RefPtr<Selection> selection = GetSelection();
+  NS_ENSURE_STATE(selection);
+
+  nsCOMPtr<nsIPresShell> presShell = GetPresShell();
+  NS_ENSURE_TRUE(presShell, NS_ERROR_NOT_INITIALIZED);
+
+  nsCOMPtr<nsISelectionController> selCon;
+  nsresult rv = GetSelectionController(getter_AddRefs(selCon));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Init the caret
+  RefPtr<nsCaret> caret = presShell->GetCaret();
+  NS_ENSURE_TRUE(caret, NS_ERROR_UNEXPECTED);
+  caret->SetIgnoreUserModify(false);
+  caret->SetSelection(selection);
+  selCon->SetCaretReadOnly(IsReadonly());
+  selCon->SetCaretEnabled(true);
+
+  // Init selection
+  selCon->SetDisplaySelection(nsISelectionController::SELECTION_ON);
+  selCon->SetSelectionFlags(nsISelectionDisplay::DISPLAY_ALL);
+  selCon->RepaintSelection(nsISelectionController::SELECTION_NORMAL);
+  // If the computed selection root isn't root content, we should set it
+  // as selection ancestor limit.  However, if that is root element, it means
+  // there is not limitation of the selection, then, we must set nullptr.
+  // NOTE: If we set a root element to the ancestor limit, some selection
+  // methods don't work fine.
+  if (selectionRootContent->GetParent()) {
+    selection->SetAncestorLimiter(selectionRootContent);
+  } else {
+    selection->SetAncestorLimiter(nullptr);
+  }
+
+  // XXX What case needs this?
+  if (isTargetDoc) {
+    int32_t rangeCount;
+    selection->GetRangeCount(&rangeCount);
+    if (!rangeCount) {
+      BeginningOfDocument();
+    }
+  }
+
+  // If there is composition when this is called, we may need to restore IME
+  // selection because if the editor is reframed, this already forgot IME
+  // selection and the transaction.
+  if (mComposition && !mIMETextNode && mIMETextLength) {
+    // We need to look for the new mIMETextNode from current selection.
+    // XXX If selection is changed during reframe, this doesn't work well!
+    nsRange* firstRange = selection->GetRangeAt(0);
+    NS_ENSURE_TRUE(firstRange, NS_ERROR_FAILURE);
+    nsCOMPtr<nsINode> startNode = firstRange->GetStartParent();
+    int32_t startOffset = firstRange->StartOffset();
+    FindBetterInsertionPoint(startNode, startOffset);
+    Text* textNode = startNode->GetAsText();
+    MOZ_ASSERT(textNode,
+               "There must be text node if mIMETextLength is larger than 0");
+    if (textNode) {
+      MOZ_ASSERT(textNode->Length() >= mIMETextOffset + mIMETextLength,
+                 "The text node must be different from the old mIMETextNode");
+      CompositionTransaction::SetIMESelection(*this, textNode, mIMETextOffset,
+                                              mIMETextLength,
+                                              mComposition->GetRanges());
+    }
+  }
+
+  return NS_OK;
+}
+
+class RepaintSelectionRunner final : public Runnable {
+public:
+  explicit RepaintSelectionRunner(nsISelectionController* aSelectionController)
+    : mSelectionController(aSelectionController)
+  {
+  }
+
+  NS_IMETHOD Run() override
+  {
+    mSelectionController->RepaintSelection(
+                            nsISelectionController::SELECTION_NORMAL);
+    return NS_OK;
+  }
+
+private:
+  nsCOMPtr<nsISelectionController> mSelectionController;
+};
+
+NS_IMETHODIMP
+EditorBase::FinalizeSelection()
+{
+  nsCOMPtr<nsISelectionController> selCon;
+  nsresult rv = GetSelectionController(getter_AddRefs(selCon));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  RefPtr<Selection> selection = GetSelection();
+  NS_ENSURE_STATE(selection);
+
+  selection->SetAncestorLimiter(nullptr);
+
+  nsCOMPtr<nsIPresShell> presShell = GetPresShell();
+  NS_ENSURE_TRUE(presShell, NS_ERROR_NOT_INITIALIZED);
+
+  selCon->SetCaretEnabled(false);
+
+  nsFocusManager* fm = nsFocusManager::GetFocusManager();
+  NS_ENSURE_TRUE(fm, NS_ERROR_NOT_INITIALIZED);
+  fm->UpdateCaretForCaretBrowsingMode();
+
+  if (!HasIndependentSelection()) {
+    // If this editor doesn't have an independent selection, i.e., it must
+    // mean that it is an HTML editor, the selection controller is shared with
+    // presShell.  So, even this editor loses focus, other part of the document
+    // may still have focus.
+    nsCOMPtr<nsIDocument> doc = GetDocument();
+    ErrorResult ret;
+    if (!doc || !doc->HasFocus(ret)) {
+      // If the document already lost focus, mark the selection as disabled.
+      selCon->SetDisplaySelection(nsISelectionController::SELECTION_DISABLED);
+    } else {
+      // Otherwise, mark selection as normal because outside of a
+      // contenteditable element should be selected with normal selection
+      // color after here.
+      selCon->SetDisplaySelection(nsISelectionController::SELECTION_ON);
+    }
+  } else if (IsFormWidget() || IsPasswordEditor() ||
+             IsReadonly() || IsDisabled() || IsInputFiltered()) {
+    // In <input> or <textarea>, the independent selection should be hidden
+    // while this editor doesn't have focus.
+    selCon->SetDisplaySelection(nsISelectionController::SELECTION_HIDDEN);
+  } else {
+    // Otherwise, although we're not sure how this case happens, the
+    // independent selection should be marked as disabled.
+    selCon->SetDisplaySelection(nsISelectionController::SELECTION_DISABLED);
+  }
+
+
+  // FinalizeSelection might be called from ContentRemoved even if selection
+  // isn't updated.  So we need to call RepaintSelection after updated it.
+  nsContentUtils::AddScriptRunner(
+                    new RepaintSelectionRunner(selCon));
+  return NS_OK;
+}
+
+Element*
+EditorBase::GetRoot()
+{
+  if (!mRootElement) {
+    // Let GetRootElement() do the work
+    nsCOMPtr<nsIDOMElement> root;
+    GetRootElement(getter_AddRefs(root));
+  }
+
+  return mRootElement;
+}
+
+Element*
+EditorBase::GetEditorRoot()
+{
+  return GetRoot();
+}
+
+Element*
+EditorBase::GetExposedRoot()
+{
+  Element* rootElement = GetRoot();
+
+  // For plaintext editors, we need to ask the input/textarea element directly.
+  if (rootElement && rootElement->IsRootOfNativeAnonymousSubtree()) {
+    rootElement = rootElement->GetParent()->AsElement();
+  }
+
+  return rootElement;
+}
+
+nsresult
+EditorBase::DetermineCurrentDirection()
+{
+  // Get the current root direction from its frame
+  nsIContent* rootElement = GetExposedRoot();
+  NS_ENSURE_TRUE(rootElement, NS_ERROR_FAILURE);
+
+  // If we don't have an explicit direction, determine our direction
+  // from the content's direction
+  if (!(mFlags & (nsIPlaintextEditor::eEditorLeftToRight |
+                  nsIPlaintextEditor::eEditorRightToLeft))) {
+    nsIFrame* frame = rootElement->GetPrimaryFrame();
+    NS_ENSURE_TRUE(frame, NS_ERROR_FAILURE);
+
+    // Set the flag here, to enable us to use the same code path below.
+    // It will be flipped before returning from the function.
+    if (frame->StyleVisibility()->mDirection == NS_STYLE_DIRECTION_RTL) {
+      mFlags |= nsIPlaintextEditor::eEditorRightToLeft;
+    } else {
+      mFlags |= nsIPlaintextEditor::eEditorLeftToRight;
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::SwitchTextDirection()
+{
+  // Get the current root direction from its frame
+  nsIContent* rootElement = GetExposedRoot();
+
+  nsresult rv = DetermineCurrentDirection();
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Apply the opposite direction
+  if (mFlags & nsIPlaintextEditor::eEditorRightToLeft) {
+    NS_ASSERTION(!(mFlags & nsIPlaintextEditor::eEditorLeftToRight),
+                 "Unexpected mutually exclusive flag");
+    mFlags &= ~nsIPlaintextEditor::eEditorRightToLeft;
+    mFlags |= nsIPlaintextEditor::eEditorLeftToRight;
+    rv = rootElement->SetAttr(kNameSpaceID_None, nsGkAtoms::dir, NS_LITERAL_STRING("ltr"), true);
+  } else if (mFlags & nsIPlaintextEditor::eEditorLeftToRight) {
+    NS_ASSERTION(!(mFlags & nsIPlaintextEditor::eEditorRightToLeft),
+                 "Unexpected mutually exclusive flag");
+    mFlags |= nsIPlaintextEditor::eEditorRightToLeft;
+    mFlags &= ~nsIPlaintextEditor::eEditorLeftToRight;
+    rv = rootElement->SetAttr(kNameSpaceID_None, nsGkAtoms::dir, NS_LITERAL_STRING("rtl"), true);
+  }
+
+  if (NS_SUCCEEDED(rv)) {
+    FireInputEvent();
+  }
+
+  return rv;
+}
+
+void
+EditorBase::SwitchTextDirectionTo(uint32_t aDirection)
+{
+  // Get the current root direction from its frame
+  nsIContent* rootElement = GetExposedRoot();
+
+  nsresult rv = DetermineCurrentDirection();
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  // Apply the requested direction
+  if (aDirection == nsIPlaintextEditor::eEditorLeftToRight &&
+      (mFlags & nsIPlaintextEditor::eEditorRightToLeft)) {
+    NS_ASSERTION(!(mFlags & nsIPlaintextEditor::eEditorLeftToRight),
+                 "Unexpected mutually exclusive flag");
+    mFlags &= ~nsIPlaintextEditor::eEditorRightToLeft;
+    mFlags |= nsIPlaintextEditor::eEditorLeftToRight;
+    rv = rootElement->SetAttr(kNameSpaceID_None, nsGkAtoms::dir, NS_LITERAL_STRING("ltr"), true);
+  } else if (aDirection == nsIPlaintextEditor::eEditorRightToLeft &&
+             (mFlags & nsIPlaintextEditor::eEditorLeftToRight)) {
+    NS_ASSERTION(!(mFlags & nsIPlaintextEditor::eEditorRightToLeft),
+                 "Unexpected mutually exclusive flag");
+    mFlags |= nsIPlaintextEditor::eEditorRightToLeft;
+    mFlags &= ~nsIPlaintextEditor::eEditorLeftToRight;
+    rv = rootElement->SetAttr(kNameSpaceID_None, nsGkAtoms::dir, NS_LITERAL_STRING("rtl"), true);
+  }
+
+  if (NS_SUCCEEDED(rv)) {
+    FireInputEvent();
+  }
+}
+
+#if DEBUG_JOE
+void
+EditorBase::DumpNode(nsIDOMNode* aNode,
+                     int32_t indent)
+{
+  for (int32_t i = 0; i < indent; i++) {
+    printf("  ");
+  }
+
+  nsCOMPtr<nsIDOMElement> element = do_QueryInterface(aNode);
+  nsCOMPtr<nsIDOMDocumentFragment> docfrag = do_QueryInterface(aNode);
+
+  if (element || docfrag) {
+    if (element) {
+      nsAutoString tag;
+      element->GetTagName(tag);
+      printf("<%s>\n", NS_LossyConvertUTF16toASCII(tag).get());
+    } else {
+      printf("<document fragment>\n");
+    }
+    nsCOMPtr<nsIDOMNodeList> childList;
+    aNode->GetChildNodes(getter_AddRefs(childList));
+    NS_ENSURE_TRUE(childList, NS_ERROR_NULL_POINTER);
+    uint32_t numChildren;
+    childList->GetLength(&numChildren);
+    nsCOMPtr<nsIDOMNode> child, tmp;
+    aNode->GetFirstChild(getter_AddRefs(child));
+    for (uint32_t i = 0; i < numChildren; i++) {
+      DumpNode(child, indent + 1);
+      child->GetNextSibling(getter_AddRefs(tmp));
+      child = tmp;
+    }
+  } else if (IsTextNode(aNode)) {
+    nsCOMPtr<nsIDOMCharacterData> textNode = do_QueryInterface(aNode);
+    nsAutoString str;
+    textNode->GetData(str);
+    nsAutoCString cstr;
+    LossyCopyUTF16toASCII(str, cstr);
+    cstr.ReplaceChar('\n', ' ');
+    printf("<textnode> %s\n", cstr.get());
+  }
+}
+#endif
+
+bool
+EditorBase::IsModifiableNode(nsIDOMNode* aNode)
+{
+  return true;
+}
+
+bool
+EditorBase::IsModifiableNode(nsINode* aNode)
+{
+  return true;
+}
+
+already_AddRefed<nsIContent>
+EditorBase::GetFocusedContent()
+{
+  nsCOMPtr<nsIDOMEventTarget> piTarget = GetDOMEventTarget();
+  if (!piTarget) {
+    return nullptr;
+  }
+
+  nsFocusManager* fm = nsFocusManager::GetFocusManager();
+  NS_ENSURE_TRUE(fm, nullptr);
+
+  nsCOMPtr<nsIContent> content = fm->GetFocusedContent();
+  return SameCOMIdentity(content, piTarget) ? content.forget() : nullptr;
+}
+
+already_AddRefed<nsIContent>
+EditorBase::GetFocusedContentForIME()
+{
+  return GetFocusedContent();
+}
+
+bool
+EditorBase::IsActiveInDOMWindow()
+{
+  nsCOMPtr<nsIDOMEventTarget> piTarget = GetDOMEventTarget();
+  if (!piTarget) {
+    return false;
+  }
+
+  nsFocusManager* fm = nsFocusManager::GetFocusManager();
+  NS_ENSURE_TRUE(fm, false);
+
+  nsCOMPtr<nsIDocument> doc = do_QueryReferent(mDocWeak);
+  nsPIDOMWindowOuter* ourWindow = doc->GetWindow();
+  nsCOMPtr<nsPIDOMWindowOuter> win;
+  nsIContent* content =
+    nsFocusManager::GetFocusedDescendant(ourWindow, false,
+                                         getter_AddRefs(win));
+  return SameCOMIdentity(content, piTarget);
+}
+
+bool
+EditorBase::IsAcceptableInputEvent(nsIDOMEvent* aEvent)
+{
+  // If the event is trusted, the event should always cause input.
+  NS_ENSURE_TRUE(aEvent, false);
+
+  WidgetEvent* widgetEvent = aEvent->WidgetEventPtr();
+  if (NS_WARN_IF(!widgetEvent)) {
+    return false;
+  }
+
+  // If this is dispatched by using cordinates but this editor doesn't have
+  // focus, we shouldn't handle it.
+  if (widgetEvent->IsUsingCoordinates()) {
+    nsCOMPtr<nsIContent> focusedContent = GetFocusedContent();
+    if (!focusedContent) {
+      return false;
+    }
+  }
+
+  // If a composition event isn't dispatched via widget, we need to ignore them
+  // since they cannot be managed by TextComposition. E.g., the event was
+  // created by chrome JS.
+  // Note that if we allow to handle such events, editor may be confused by
+  // strange event order.
+  bool needsWidget = false;
+  WidgetGUIEvent* widgetGUIEvent = nullptr;
+  switch (widgetEvent->mMessage) {
+    case eUnidentifiedEvent:
+      // If events are not created with proper event interface, their message
+      // are initialized with eUnidentifiedEvent.  Let's ignore such event.
+      return false;
+    case eCompositionStart:
+    case eCompositionEnd:
+    case eCompositionUpdate:
+    case eCompositionChange:
+    case eCompositionCommitAsIs:
+      // Don't allow composition events whose internal event are not
+      // WidgetCompositionEvent.
+      widgetGUIEvent = aEvent->WidgetEventPtr()->AsCompositionEvent();
+      needsWidget = true;
+      break;
+    default:
+      break;
+  }
+  if (needsWidget &&
+      (!widgetGUIEvent || !widgetGUIEvent->mWidget)) {
+    return false;
+  }
+
+  // Accept all trusted events.
+  if (widgetEvent->IsTrusted()) {
+    return true;
+  }
+
+  // Ignore untrusted mouse event.
+  // XXX Why are we handling other untrusted input events?
+  if (widgetEvent->AsMouseEventBase()) {
+    return false;
+  }
+
+  // Otherwise, we shouldn't handle any input events when we're not an active
+  // element of the DOM window.
+  return IsActiveInDOMWindow();
+}
+
+void
+EditorBase::OnFocus(nsIDOMEventTarget* aFocusEventTarget)
+{
+  InitializeSelection(aFocusEventTarget);
+  if (mInlineSpellChecker) {
+    mInlineSpellChecker->UpdateCurrentDictionary();
+  }
+}
+
+NS_IMETHODIMP
+EditorBase::GetSuppressDispatchingInputEvent(bool* aSuppressed)
+{
+  NS_ENSURE_ARG_POINTER(aSuppressed);
+  *aSuppressed = !mDispatchInputEvent;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::SetSuppressDispatchingInputEvent(bool aSuppress)
+{
+  mDispatchInputEvent = !aSuppress;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+EditorBase::GetIsInEditAction(bool* aIsInEditAction)
+{
+  MOZ_ASSERT(aIsInEditAction, "aIsInEditAction must not be null");
+  *aIsInEditAction = mIsInEditAction;
+  return NS_OK;
+}
+
+int32_t
+EditorBase::GetIMESelectionStartOffsetIn(nsINode* aTextNode)
+{
+  MOZ_ASSERT(aTextNode, "aTextNode must not be nullptr");
+
+  nsCOMPtr<nsISelectionController> selectionController;
+  nsresult rv = GetSelectionController(getter_AddRefs(selectionController));
+  NS_ENSURE_SUCCESS(rv, -1);
+  NS_ENSURE_TRUE(selectionController, -1);
+
+  int32_t minOffset = INT32_MAX;
+  static const SelectionType kIMESelectionTypes[] = {
+    SelectionType::eIMERawClause,
+    SelectionType::eIMESelectedRawClause,
+    SelectionType::eIMEConvertedClause,
+    SelectionType::eIMESelectedClause
+  };
+  for (auto selectionType : kIMESelectionTypes) {
+    RefPtr<Selection> selection = GetSelection(selectionType);
+    if (!selection) {
+      continue;
+    }
+    for (uint32_t i = 0; i < selection->RangeCount(); i++) {
+      RefPtr<nsRange> range = selection->GetRangeAt(i);
+      if (NS_WARN_IF(!range)) {
+        continue;
+      }
+      if (NS_WARN_IF(range->GetStartParent() != aTextNode)) {
+        // ignore the start offset...
+      } else {
+        MOZ_ASSERT(range->StartOffset() >= 0,
+                   "start offset shouldn't be negative");
+        minOffset = std::min(minOffset, range->StartOffset());
+      }
+      if (NS_WARN_IF(range->GetEndParent() != aTextNode)) {
+        // ignore the end offset...
+      } else {
+        MOZ_ASSERT(range->EndOffset() >= 0,
+                   "start offset shouldn't be negative");
+        minOffset = std::min(minOffset, range->EndOffset());
+      }
+    }
+  }
+  return minOffset < INT32_MAX ? minOffset : -1;
+}
+
+void
+EditorBase::HideCaret(bool aHide)
+{
+  if (mHidingCaret == aHide) {
+    return;
+  }
+
+  nsCOMPtr<nsIPresShell> presShell = GetPresShell();
+  NS_ENSURE_TRUE_VOID(presShell);
+  RefPtr<nsCaret> caret = presShell->GetCaret();
+  NS_ENSURE_TRUE_VOID(caret);
+
+  mHidingCaret = aHide;
+  if (aHide) {
+    caret->AddForceHide();
+  } else {
+    caret->RemoveForceHide();
+  }
+}
+
+} // namespace mozilla