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

cc/input/input_handler.h

Index: cc/input/input_handler.h
diff --git a/cc/input/input_handler.h b/cc/input/input_handler.h
index 9b96db789d1d03c4a5fc6fc655288ffb3ad0f0d1..9d0ce6795b4c4e790a57ea87069ea72bfa74d79e 100644
--- a/cc/input/input_handler.h
+++ b/cc/input/input_handler.h
@@ -105,6 +105,12 @@ class CC_EXPORT InputHandler {
     NON_BUBBLING_GESTURE
   };
 
+  enum TouchEventDisposition {

[bokan, 2016/11/17 15:39:28]

This looks unused?

[lanwei, 2016/11/18 00:54:07]

Acknowledged.

+    HANDLE,
+    NOT_HANDLE,
+    NOT_HANDLE_NON_BLOCKING_DUE_TO_FLING
+  };
+
   // Binds a client to this handler to receive notifications. Only one client
   // can be bound to an InputHandler. The client must live at least until the
   // handler calls WillShutdown() on the client.
@@ -188,9 +194,12 @@ class CC_EXPORT InputHandler {
   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