Make touch events uncancelable during fling when they are on the current active scroll layer

cc/input/input_handler.h

 // Copyright 2011 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 CC_INPUT_INPUT_HANDLER_H_
 #define CC_INPUT_INPUT_HANDLER_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 170 matching lines @@
   // Returns true if there is an active scroll on the viewport.
   virtual bool IsCurrentlyScrollingViewport() const = 0;
 
   // Whether the layer under |viewport_point| is the currently scrolling layer.
   virtual bool IsCurrentlyScrollingLayerAt(const gfx::Point& viewport_point,
                                            ScrollInputType type) const = 0;
 
   virtual EventListenerProperties GetEventListenerProperties(
       EventListenerClass event_class) const = 0;
 
-  // Whether the page should be given the opportunity to suppress scrolling by
-  // consuming touch events that started at |viewport_point|.
-  virtual bool DoTouchEventsBlockScrollAt(const gfx::Point& viewport_point) = 0;
+  // It returns the type of event listener at the given viewport point. Such as
+  // if the page has a touch handler or not, and whether the page should
+  // suppress scrolling by consuming touch events that started at
+  // |viewport_point|.
+  virtual EventListenerProperties EventListenerTypeForTouchStartAt(
+      const gfx::Point& viewport_point) = 0;
 
   // Calling CreateLatencyInfoSwapPromiseMonitor() to get a scoped
   // LatencyInfoSwapPromiseMonitor. During the life time of the
   // LatencyInfoSwapPromiseMonitor, if SetNeedsRedraw() or SetNeedsRedrawRect()
   // is called on LayerTreeHostImpl, the original latency info will be turned
   // into a LatencyInfoSwapPromise.
   virtual std::unique_ptr<SwapPromiseMonitor>
   CreateLatencyInfoSwapPromiseMonitor(ui::LatencyInfo* latency) = 0;
 
   virtual ScrollElasticityHelper* CreateScrollElasticityHelper() = 0;
 
   // Called by the single-threaded UI Compositor to get or set the scroll offset
   // on the impl side. Retruns false if |layer_id| isn't in the active tree.
   virtual bool GetScrollOffsetForLayer(int layer_id,
                                        gfx::ScrollOffset* offset) = 0;
   virtual bool ScrollLayerTo(int layer_id, const gfx::ScrollOffset& offset) = 0;
 
  protected:
   InputHandler() {}
   virtual ~InputHandler() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(InputHandler);
 };
 
 }  // namespace cc
 
 #endif  // CC_INPUT_INPUT_HANDLER_H_