Notify Blink about start of gesture scroll through a queued event.

third_party/WebKit/Source/core/input/PointerEventManager.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef PointerEventManager_h
 #define PointerEventManager_h
 
 #include "core/CoreExport.h"
 #include "core/events/PointerEvent.h"
 #include "core/events/PointerEventFactory.h"
@@ skipping 21 matching lines @@
         AbstractView*,
         Node* lastNodeUnderMouse);
 
     // Returns whether the event is consumed or not
     WebInputEventResult sendTouchPointerEvent(
         EventTarget*,
         const PlatformTouchPoint&, PlatformEvent::Modifiers,
         const double width, const double height,
         const double clientX, const double clientY);
 
-    void sendTouchCancelPointerEvent(EventTarget*,
-        const PlatformTouchPoint&);
+    // Inhibits firing of touch-type PointerEvents until unblocked by unblockTouchPointers(). Also
+    // sends pointercancels for existing touch-type PointerEvents.
+    // See: www.w3.org/TR/pointerevents/#declaring-candidate-regions-for-default-touch-behaviors
+    void blockTouchPointers();
+
+    // Enables firing of touch-type PointerEvents after they were inhibited by blockTouchPointers().
+    void unblockTouchPointers();
 
     // Sends node transition events mouseout/leave/over/enter to the
     // corresponding targets. This function sends pointerout/leave/over/enter
     // only when isFrameBoundaryTransition is true which indicates the
     // transition is over the document boundary and not only the elements border
     // inside the document. If isFrameBoundaryTransition is false,
     // then the event is a compatibility event like those created by touch
     // and in that case the corresponding pointer events will be handled by
     // sendTouchPointerEvent for example and there is no need to send pointer
     // transition events. Note that normal mouse events (e.g. mousemove/down/up)
@@ skipping 74 matching lines @@
         EventTarget*,
         PointerEvent*,
         bool checkForListener = false);
     void releasePointerCapture(int);
 
     // Prevents firing mousedown, mousemove & mouseup in-between a canceled pointerdown and next pointerup/pointercancel.
     // See "PREVENT MOUSE EVENT flag" in the spec:
     //   https://w3c.github.io/pointerevents/#compatibility-mapping-with-mouse-events
     bool m_preventMouseEventForPointerType[static_cast<size_t>(WebPointerProperties::PointerType::LastEntry) + 1];
 
+    // Set upon sending a pointercancel for touch, prevents PE dispatches for touches until
+    // all touch-points become inactive.
+    bool m_inCanceledStateForPointerTypeTouch;
+
     // Note that this map keeps track of node under pointer with id=1 as well
     // which might be different than m_nodeUnderMouse in EventHandler. That one
     // keeps track of any compatibility mouse event positions but this map for
     // the pointer with id=1 is only taking care of true mouse related events.
     HeapHashMap<int, EventTargetAttributes> m_nodeUnderPointer;
 
     PointerCapturingMap m_pointerCaptureTarget;
     PointerCapturingMap m_pendingPointerCaptureTarget;
     PointerEventFactory m_pointerEventFactory;
 };
 
 } // namespace blink
 
 #endif // PointerEventManager_h