Expose whether a touch event may cause scrolling if uncanceled

public/web/WebInputEvent.h

 /*
  * Copyright (C) 2009 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 148 matching lines @@
 
         // Toggle modifiers for all events. Danger: these are not reflected
         // into WebCore, so round-tripping from WebInputEvent to a WebCore
         // event and back will not preserve these flags.
         CapsLockOn       = 1 << 9,
         NumLockOn        = 1 << 10,
 
         // Left/right modifiers for keyboard events.
         IsLeft           = 1 << 11,
         IsRight          = 1 << 12,
-
-        // Last input event to be sent for the current vsync interval. If this
-        // flag is set, the sender guarantees that no more input events will be
-        // delivered until the next vsync and the receiver can schedule
-        // rendering accordingly. If it isn't set, the receiver should not make
-        // any assumptions about the delivery times of future input events
-        // w.r.t. vsync.
-        IsLastInputEventForCurrentVSync = 1 << 13,
     };
 
     static const int InputModifiers = ShiftKey | ControlKey | AltKey | MetaKey;
 
     double timeStampSeconds; // Seconds since epoch.
     unsigned size; // The size of this structure, for serialization.
     Type type;
     int modifiers;
 
     // Returns true if the WebInputEvent |type| is a mouse event.
@@ skipping 302 matching lines @@
 
     unsigned touchesLength;
     // List of all touches, regardless of state.
     WebTouchPoint touches[touchesLengthCap];
 
     // Whether the event can be canceled (with preventDefault). If true then the browser
     // must wait for an ACK for this event. If false then no ACK IPC is expected.
     // See comment at the top for why an int is used here instead of a bool.
     int cancelable;
 
+    // Whether the event may cause scrolling if not canceled. This will be true
+    // for touchmove events after the platform slop region has been exceeded
+    // and touchend events that induce a fling.
+    // See comment at the top for why an int is used here instead of a bool.
+    int mayCauseScrollingIfUncanceled;

[Rick Byers, 2014/11/10 18:56:04]

Nit: if it really "will be true for ..." then why call it "may..."?  Maybe just
"causesScrollingIfUncanceled"?

Do you plan to take the touch-action filter into account in setting this bit?

+
     WebTouchEvent()
         : WebInputEvent(sizeof(WebTouchEvent))
         , touchesLength(0)
         , cancelable(true)
+        , mayCauseScrollingIfUncanceled(false)
     {
     }
 };
 
 #pragma pack(pop)
 
 } // namespace blink
 
 #endif