Add sequence number to undo steps

third_party/WebKit/Source/core/editing/commands/CompositeEditCommand.h

 /*
  * Copyright (C) 2005, 2006, 2008 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 37 matching lines @@
  public:
   static EditCommandComposition* create(Document*,
                                         const VisibleSelection&,
                                         const VisibleSelection&,
                                         InputEvent::InputType);
 
   bool belongsTo(const LocalFrame&) const override;
   void unapply() override;
   void reapply() override;
   InputEvent::InputType inputType() const override;
+  int sequence() const override;
+  void setSequence(int) override;
+
   void append(SimpleEditCommand*);
   void append(EditCommandComposition*);
 
   const VisibleSelection& startingSelection() const {
     return m_startingSelection;
   }
   const VisibleSelection& endingSelection() const { return m_endingSelection; }
   void setStartingSelection(const VisibleSelection&);
   void setEndingSelection(const VisibleSelection&);
   Element* startingRootEditableElement() const {
@@ skipping 11 matching lines @@
                          const VisibleSelection& endingSelection,
                          InputEvent::InputType);
 
   Member<Document> m_document;
   VisibleSelection m_startingSelection;
   VisibleSelection m_endingSelection;
   HeapVector<Member<SimpleEditCommand>> m_commands;
   Member<Element> m_startingRootEditableElement;
   Member<Element> m_endingRootEditableElement;
   InputEvent::InputType m_inputType;
+  int m_sequence;
 };
 
 class CORE_EXPORT CompositeEditCommand : public EditCommand {
  public:
   enum ShouldPreserveSelection { PreserveSelection, DoNotPreserveSelection };
   enum ShouldPreserveStyle { PreserveStyle, DoNotPreserveStyle };
 
   ~CompositeEditCommand() override;
 
   // Returns |false| if the command failed.  e.g. It's aborted.
@@ skipping 173 matching lines @@
 
 DEFINE_TYPE_CASTS(CompositeEditCommand,
                   EditCommand,
                   command,
                   command->isCompositeEditCommand(),
                   command.isCompositeEditCommand());
 
 }  // namespace blink
 
 #endif  // CompositeEditCommand_h