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..9630e81e759da3f8f20fb2d4f7c79427a0856bcd 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 {
+    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 +194,11 @@ 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 if the page has a touch handler or not. If it has, whether the
+  // page should suppress scrolling by consuming touch events that started at
+  // |viewport_point|.
+  virtual EventListenerProperties DoTouchHandlersBlockScrollAt(

[bokan, 2016/11/15 22:42:40]

Do____ implies the method returns a bool. I would rename this to
TouchHandlerTypeAt. The comment could also be improved: it returns the type of
event listener at the given viewport point.

[lanwei, 2016/11/16 21:13:28]

Done.

+      const gfx::Point& viewport_point) = 0;
 
   // Calling CreateLatencyInfoSwapPromiseMonitor() to get a scoped
   // LatencyInfoSwapPromiseMonitor. During the life time of the