[LayoutTest] Fix flakey test "inputevent-drag-drop.html"

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

 /*
  * Copyright (C) 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 282 matching lines @@
     command->setEndingSelection(selection);
   }
   command->doApply(editingState);
   if (!editingState->isAborted())
     m_commands.append(command);
 }
 
 void CompositeEditCommand::appendCommandToComposite(
     CompositeEditCommand* command) {
   ensureComposition()->append(command->ensureComposition());
+  command->m_composition = nullptr;

[yosin_UTC9, 2016/10/06 01:22:09]

This is right place to fix.
I hit DCHECK(isTopLevelCommand() || !m_composition) in CompositeEditCommand dtor
running layout test.
If you run layout test --enable-leak-detection more layout test hit DCHECK in
dtor.
Anyway, thanks for fixing this!

   command->setParent(this);
   m_commands.append(command);
 }
 
 void CompositeEditCommand::applyStyle(const EditingStyle* style,
                                       EditingState* editingState) {
   applyCommandToComposite(
       ApplyStyleCommand::create(document(), style,
                                 InputEvent::InputType::ChangeAttributes),
       editingState);
@@ skipping 1628 matching lines @@
   return node;
 }
 
 DEFINE_TRACE(CompositeEditCommand) {
   visitor->trace(m_commands);
   visitor->trace(m_composition);
   EditCommand::trace(visitor);
 }
 
 }  // namespace blink