Articulate the cancel behavior in the WebTouchEvent.

content/renderer/input/main_thread_event_queue.cc

 // Copyright 2016 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 "content/renderer/input/main_thread_event_queue.h"
 
 namespace content {
 
 MainThreadEventQueue::MainThreadEventQueue(int routing_id,
                                            MainThreadEventQueueClient* client)
@@ skipping 30 matching lines @@
                                        dispatch_type);
       } else {
         // If there is nothing in the event queue and the event is
         // blocking pass the |original_dispatch_type| to avoid
         // having the main thread call us back as an optimization.
         client_->SendEventToMainThread(routing_id_, event, latency,
                                        original_dispatch_type);
       }
     }
   } else if (blink::WebInputEvent::isTouchEventType(event->type)) {
+    PendingTouchEvent modified_dispatch_type_event =
+        PendingTouchEvent(*static_cast<const blink::WebTouchEvent*>(event),
+                          latency, dispatch_type);
+
+    // Adjust the |dispatchType| on the event since it was
+    // adjusted by the compositor.

[tdresser, 2016/04/20 13:20:21]

Maybe "since the compositor determined all event listeners are passive."?

[dtapuska, 2016/04/20 13:56:34]

Done.

+    if (non_blocking) {
+      modified_dispatch_type_event.event.dispatchType =
+          blink::WebInputEvent::ListenersNonBlockingPassive;
+    }
+
     if (touch_events_.state() == WebInputEventQueueState::ITEM_PENDING) {
-      touch_events_.Queue(
-          PendingTouchEvent(*static_cast<const blink::WebTouchEvent*>(event),
-                            latency, dispatch_type));
+      touch_events_.Queue(modified_dispatch_type_event);
     } else {
       if (non_blocking) {
         touch_events_.set_state(WebInputEventQueueState::ITEM_PENDING);
-        client_->SendEventToMainThread(routing_id_, event, latency,
-                                       dispatch_type);
+        client_->SendEventToMainThread(routing_id_,
+                                       &modified_dispatch_type_event.event,
+                                       latency, dispatch_type);
       } else {
         // If there is nothing in the event queue and the event is
         // blocking pass the |original_dispatch_type| to avoid
         // having the main thread call us back as an optimization.
-        client_->SendEventToMainThread(routing_id_, event, latency,
-                                       original_dispatch_type);
+        client_->SendEventToMainThread(routing_id_,
+                                       &modified_dispatch_type_event.event,
+                                       latency, original_dispatch_type);
       }
     }
   } else {
     client_->SendEventToMainThread(routing_id_, event, latency,
                                    original_dispatch_type);
   }
 
   // send an ack when we are non-blocking.
   return non_blocking;
 }
@@ skipping 14 matching lines @@
                                      event->type);
     } else {
       touch_events_.set_state(WebInputEventQueueState::ITEM_NOT_PENDING);
     }
   } else {
     NOTREACHED() << "Invalid passive event type";
   }
 }
 
 }  // namespace content