[InputEvent] Support |deleteByDrag|, |insertFromDrop| and fire in sequential order

third_party/WebKit/Source/core/editing/commands/EditCommand.cpp

 /*
  * Copyright (C) 2005, 2006, 2007 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 94 matching lines @@
     LayoutObject* layoutObject = position.anchorNode()->layoutObject();
     if (!layoutObject)
         return false;
 
     return toLayoutText(layoutObject)->isRenderedCharacter(position.offsetInContainerNode());
 }
 
 void EditCommand::setParent(CompositeEditCommand* parent)
 {
     DCHECK((parent && !m_parent) || (!parent && m_parent));
-    DCHECK(!parent || !isCompositeEditCommand() || !toCompositeEditCommand(this)->composition());
+    // Only allow merging |InsertFromDrop| with previous |DeleteByDrag| after applied.
+    DCHECK(!parent || !isCompositeEditCommand() || inputType() == InputEvent::InputType::InsertFromDrop || !toCompositeEditCommand(this)->composition());
     m_parent = parent;
     if (parent) {
         m_startingSelection = parent->m_endingSelection;
         m_endingSelection = parent->m_endingSelection;
     }
 }
 
 void SimpleEditCommand::doReapply()
 {
     EditingState editingState;
     doApply(&editingState);
 }
 
 DEFINE_TRACE(EditCommand)
 {
     visitor->trace(m_document);
     visitor->trace(m_startingSelection);
     visitor->trace(m_endingSelection);
     visitor->trace(m_parent);
 }
 
 } // namespace blink