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

ui/events/blink/input_handler_proxy.cc

Index: ui/events/blink/input_handler_proxy.cc
diff --git a/ui/events/blink/input_handler_proxy.cc b/ui/events/blink/input_handler_proxy.cc
index ae52f930a7bb120dafa969c6e244855a4024e0e6..d4d40a6a4ec22b2ad916e1e2fef608a2e28d638d 100644
--- a/ui/events/blink/input_handler_proxy.cc
+++ b/ui/events/blink/input_handler_proxy.cc
@@ -935,12 +935,19 @@ InputHandlerProxy::EventDisposition InputHandlerProxy::HandleGestureFlingStart(
 InputHandlerProxy::EventDisposition InputHandlerProxy::HandleTouchStart(
     const blink::WebTouchEvent& touch_event) {
   EventDisposition result = DROP_EVENT;
+  bool maybe_passive_due_to_fling = false;

[tdresser, 2016/11/24 19:53:41]

What does this bool actually mean? Should this be |touching_scrolling_layer| or
something like that?

[lanwei, 2016/11/24 20:28:01]

Done.

   for (size_t i = 0; i < touch_event.touchesLength; ++i) {
     if (touch_event.touches[i].state != WebTouchPoint::StatePressed)
       continue;
-    if (input_handler_->DoTouchEventsBlockScrollAt(
+    cc::InputHandler::TouchStartEventListenerType event_listener_type =
+        input_handler_->EventListenerTypeForTouchStartAt(
             gfx::Point(touch_event.touches[i].position.x,
-                       touch_event.touches[i].position.y))) {
+                       touch_event.touches[i].position.y));
+    if (event_listener_type !=
+        cc::InputHandler::TouchStartEventListenerType::NO_HANDLER) {
+      maybe_passive_due_to_fling =
+          event_listener_type == cc::InputHandler::TouchStartEventListenerType::
+                                     HANDLER_ON_FLINGING_LAYER;
       result = DID_NOT_HANDLE;
       break;
     }
@@ -992,7 +999,7 @@ InputHandlerProxy::EventDisposition InputHandlerProxy::HandleTouchStart(
   }
 
   bool is_fling_on_impl = fling_curve_ && !fling_may_be_active_on_main_thread_;
-  if (result == DID_NOT_HANDLE && is_fling_on_impl)
+  if (is_fling_on_impl && maybe_passive_due_to_fling)
     result = DID_NOT_HANDLE_NON_BLOCKING_DUE_TO_FLING;
 
   return result;