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

third_party/WebKit/Source/platform/PlatformEvent.h

 /*
  * Copyright (C) 2011 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 112 matching lines @@
 
     // These values are direct mappings of the values in WebInputEvent
     // so the values can be cast between the enumerations. static_asserts
     // checking this are in web/WebInputEventConversion.cpp.
     enum DispatchType {
         Blocking,
         EventNonBlocking,
         // All listeners are passive.
         ListenersNonBlockingPassive,
         // This value represents a state which would have normally blocking
-        // but was forced to be non-blocking.
-        ListenersForcedNonBlockingPassive,
+        // but was forced to be non-blocking during fling; not cancelable.
+        ListenersForcedNonBlockingPassiveDueToFling,

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

Are we considering these passive, or non-cancellable, or both?

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

I think they are passive and also non-cancellable. All passive events are not
cancelable. Not sure if we should replace passive with non-cancellable.

[tdresser, 2016/08/18 12:43:53]

I think I'd prefer if the word "Passive" only referred to event listeners which
the developer explicitly opted in to being passive.

Ideally this would hold true in the feedback devtools provided as well.

     };
 
     EventType type() const { return static_cast<EventType>(m_type); }
 
     bool shiftKey() const { return m_modifiers & ShiftKey; }
     bool ctrlKey() const { return m_modifiers & CtrlKey; }
     bool altKey() const { return m_modifiers & AltKey; }
     bool metaKey() const { return m_modifiers & MetaKey; }
 
     Modifiers getModifiers() const { return static_cast<Modifiers>(m_modifiers); }
@@ skipping 29 matching lines @@
     }
 
     unsigned m_type;
     unsigned m_modifiers;
     double m_timestamp;
 };
 
 } // namespace blink
 
 #endif // PlatformEvent_h