CANCEL: Make "compositionstart" event cancelable

Source/core/editing/InputMethodController.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  *
  * 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
@@ skipping 241 matching lines @@
         //    Send a compositionupdate event when this function updates the existing composition
         //    node, i.e. m_compositionNode != 0 && !text.isEmpty().
         // 3. Canceling the ongoing composition.
         //    Send a compositionend event when function deletes the existing composition node, i.e.
         //    m_compositionNode != 0 && test.isEmpty().
         RefPtrWillBeRawPtr<CompositionEvent> event = nullptr;
         if (!hasComposition()) {
             // We should send a compositionstart event only when the given text is not empty because this
             // function doesn't create a composition node when the text is empty.
             if (!text.isEmpty()) {
-                target->dispatchEvent(CompositionEvent::create(EventTypeNames::compositionstart, m_frame.domWindow(), m_frame.selectedText(), underlines));
+                RefPtrWillBeRawPtr<CompositionEvent> compositionStartEvent = CompositionEvent::create(EventTypeNames::compositionstart, m_frame.domWindow(), m_frame.selectedText(), underlines);
+                if (!target->dispatchEvent(compositionStartEvent)) {
+                    RefPtrWillBeRawPtr<CompositionEvent> compositionEndEvent = CompositionEvent::create(EventTypeNames::compositionend, m_frame.domWindow(), emptyString(), Vector<CompositionUnderline>());
+                    target->dispatchEvent(compositionEndEvent, IGNORE_EXCEPTION);
+                    return;
+                }
                 event = CompositionEvent::create(EventTypeNames::compositionupdate, m_frame.domWindow(), text, underlines);
             }
         } else {
             if (!text.isEmpty())
                 event = CompositionEvent::create(EventTypeNames::compositionupdate, m_frame.domWindow(), text, underlines);
             else
                 event = CompositionEvent::create(EventTypeNames::compositionend, m_frame.domWindow(), text, underlines);
         }
         if (event.get())
             target->dispatchEvent(event, IGNORE_EXCEPTION);
@@ skipping 125 matching lines @@
     if (!editor().canEdit())
         return;
     PlainTextRange selectionOffsets(getSelectionOffsets());
     if (selectionOffsets.isNull())
         return;
     setSelectionOffsets(PlainTextRange(std::max(static_cast<int>(selectionOffsets.start()) - before, 0), selectionOffsets.end() + after));
     TypingCommand::deleteSelection(*m_frame.document());
 }
 
 } // namespace WebCore