Adjust cancelabilty of touchmoves that are queued when scroll start occurs

content/renderer/input/main_thread_event_queue_task.h

 // Copyright 2017 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.
 
 #ifndef CONTENT_RENDERER_INPUT_MAIN_THREAD_EVENT_QUEUE_TASK_H_
 #define CONTENT_RENDERER_INPUT_MAIN_THREAD_EVENT_QUEUE_TASK_H_
 
 #include "content/common/input/input_event_ack_state.h"
 #include "third_party/WebKit/public/platform/WebInputEvent.h"
 #include "third_party/WebKit/public/platform/scheduler/renderer/renderer_scheduler.h"
 
 namespace content {
 
 class MainThreadEventQueueClient;
 
 // A work item to execute from the main thread event queue.
 // The MainThreadEventQueue supports 2 types of tasks (subclasses):
 // 1) Closures
 // 2) WebInputEvent
 class MainThreadEventQueueTask {
  public:
   virtual ~MainThreadEventQueueTask() {}
 
-  enum class CoalesceResult {
-    Coalesced,
-    CannotCoalesce,
-    // Keep iterating on the queue looking for a matching event with the
-    // same modality.
-    KeepSearching,
+  enum class NotifyResult {
+    CoalescedEvent,
+    Stop,
+    KeepIterating,
   };
 
-  virtual CoalesceResult CoalesceWith(const MainThreadEventQueueTask&) = 0;
+  // Notify an event will be queued. Acceptable actions are to coalesce the
+  // event with this event, stop iterating or keep iterating.

[tdresser, 2017/03/31 19:31:02]

This naming is confusing. We aren't notifying an event will be queued, cause we
might not queue it, we might coalesce it. It also isn't really clear from the
comment what it means to keep iterating here.

[dtapuska, 2017/03/31 20:18:18]

I adjusted the names a bit

+  virtual NotifyResult NotifyEventWillBeQueued(
+      const MainThreadEventQueueTask&) = 0;
   virtual bool IsWebInputEvent() const = 0;
   virtual void Dispatch(int routing_id, MainThreadEventQueueClient*) = 0;
+
   virtual void EventHandled(
       int routing_id,
       blink::scheduler::RendererScheduler* renderer_scheduler,
       MainThreadEventQueueClient* client,
       blink::WebInputEvent::Type type,
       blink::WebInputEventResult result,
       InputEventAckState ack_result) = 0;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_INPUT_MAIN_THREAD_EVENT_QUEUE_TASK_H_