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

ui/events/blink/input_handler_proxy.cc

 // Copyright 2013 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.
 
 #include "ui/events/blink/input_handler_proxy.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 
@@ skipping 817 matching lines @@
       }
       return DROP_EVENT;
     }
   }
   return DID_NOT_HANDLE;
 }
 
 InputHandlerProxy::EventDisposition InputHandlerProxy::HandleTouchStart(
     const blink::WebTouchEvent& touch_event) {
   EventDisposition result = DROP_EVENT;
+  bool maybe_passive_due_to_fling = false;
   for (size_t i = 0; i < touch_event.touchesLength; ++i) {
     if (touch_event.touches[i].state != WebTouchPoint::StatePressed)
       continue;
-    if (input_handler_->DoTouchEventsBlockScrollAt(
+    cc::EventListenerProperties event_result =
+        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_result != cc::EventListenerProperties::kNone) {
+      maybe_passive_due_to_fling =
+          event_result ==
+          cc::EventListenerProperties::kBlockingAndMaybePassiveDueToFling;
       result = DID_NOT_HANDLE;
       break;
     }
   }
 
   // If |result| is DROP_EVENT it wasn't processed above.
   if (result == DROP_EVENT) {
     switch (input_handler_->GetEventListenerProperties(
         cc::EventListenerClass::kTouchStartOrMove)) {
       case cc::EventListenerProperties::kPassive:
@@ skipping 31 matching lines @@
   // code is explicitly after the assignment of the |touch_start_result_|
   // so the touch moves are not sent to the main thread un-necessarily.
   if (result == DROP_EVENT &&
       input_handler_->GetEventListenerProperties(
           cc::EventListenerClass::kTouchEndOrCancel) !=
           cc::EventListenerProperties::kNone) {
     result = DID_HANDLE_NON_BLOCKING;
   }
 
   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;
 }
 
 InputHandlerProxy::EventDisposition InputHandlerProxy::HandleTouchMove(
     const blink::WebTouchEvent& touch_event) {
   if (touch_start_result_ != kEventDispositionUndefined)
     return static_cast<EventDisposition>(touch_start_result_);
   return DID_NOT_HANDLE;
@@ skipping 510 matching lines @@
   // is made asynchronously, to minimize divergence between main thread and
   // impl thread event handling paths.
   base::ThreadTaskRunnerHandle::Get()->PostTask(
       FROM_HERE,
       base::Bind(&InputScrollElasticityController::ObserveGestureEventAndResult,
                  scroll_elasticity_controller_->GetWeakPtr(), gesture_event,
                  scroll_result));
 }
 
 }  // namespace ui