Make first TouchStart and first TouchMove events on a flinging layer non-blocking

third_party/WebKit/Source/core/events/Event.h

 /*
  * Copyright (C) 2001 Peter Kelly (pmk@post.com)
  * Copyright (C) 2001 Tobias Anton (anton@stud.fbi.fh-darmstadt.de)
  * Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 197 matching lines @@
 
     virtual EventDispatchMediator* createMediator();
 
     bool isTrusted() const { return m_isTrusted; }
     void setTrusted(bool value) { m_isTrusted = value; }
 
     void setHandlingPassive(bool value);
 
     bool preventDefaultCalledDuringPassive() const { return m_preventDefaultCalledDuringPassive; }
 
+    bool preventDefaultCalledOnUncancelableEvent() const { return m_preventDefaultCalledOnUncancelableEvent; }
+
     DECLARE_VIRTUAL_TRACE();
 
 protected:
     Event();
     Event(const AtomicString& type, bool canBubble, bool cancelable, ComposedMode, double platformTimeStamp);
     Event(const AtomicString& type, bool canBubble, bool cancelable, double platformTimeStamp);
     Event(const AtomicString& type, bool canBubble, bool cancelable, ComposedMode = ComposedMode::Scoped);
     Event(const AtomicString& type, const EventInit&);
 
     virtual void receivedTarget();
@@ skipping 20 matching lines @@
     unsigned m_defaultPrevented:1;
     unsigned m_defaultHandled:1;
     unsigned m_cancelBubble:1;
     unsigned m_wasInitialized:1;
     unsigned m_isTrusted : 1;
     unsigned m_handlingPassive : 1;
 
     // Whether preventDefault was called when |m_handlingPassive| is
     // true. This field is reset on each call to setHandlingPassive.
     unsigned m_preventDefaultCalledDuringPassive : 1;
+    // Whether preventDefault was called on uncancelable event.
+    unsigned m_preventDefaultCalledOnUncancelableEvent : 1;

[tdresser, 2016/08/17 14:32:28]

This is a bit confusing. Are these events passive, or uncancellable?

Perhaps the dispatch type should be "ForcedUncancellable" not "ForcedPassive"?

[dtapuska, 2016/08/17 18:54:59]

These events aren't really passive. They are forced uncancellable. I agree we
need to clarify this.

[lanwei, 2016/08/18 12:31:47]

Delete passive or use uncancellable, non-blocking.

 
     unsigned short m_eventPhase;
     Member<EventTarget> m_currentTarget;
     Member<EventTarget> m_target;
     Member<Event> m_underlyingEvent;
     Member<EventPath> m_eventPath;
     // The monotonic platform time in seconds, for input events it is the
     // event timestamp provided by the host OS and reported in the original
     // WebInputEvent instance.
     double m_platformTimeStamp;
 };
 
 #define DEFINE_EVENT_TYPE_CASTS(typeName) \
     DEFINE_TYPE_CASTS(typeName, Event, event, event->is##typeName(), event.is##typeName())
 
 } // namespace blink
 
 #endif // Event_h