Articulate the cancel behavior in the WebTouchEvent.

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 103 matching lines @@
         // and don't indicate explicit depressed state.
         KeyModifiers = SymbolKey | FnKey | OSKey | AltGrKey | MetaKey | AltKey | CtrlKey | ShiftKey,
     };
 
     enum RailsMode {
         RailsModeFree       = 0,
         RailsModeHorizontal = 1,
         RailsModeVertical   = 2,
     };
 
+    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,
+    };
+
     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); }
 
     double timestamp() const { return m_timestamp; }
@@ skipping 27 matching lines @@
     }
 
     unsigned m_type;
     unsigned m_modifiers;
     double m_timestamp;
 };
 
 } // namespace blink
 
 #endif // PlatformEvent_h