Plumb firing passive event listeners.

content/renderer/input/passive_event_queue.h

+// 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.
+
+#ifndef CONTENT_RENDERER_INPUT_PASSIVE_EVENT_QUEUE_H_
+#define CONTENT_RENDERER_INPUT_PASSIVE_EVENT_QUEUE_H_
+
+#include <deque>
+#include "content/common/input/event_with_latency_info.h"
+#include "content/renderer/input/web_input_event_queue.h"
+#include "third_party/WebKit/public/web/WebInputEvent.h"
+#include "ui/events/latency_info.h"
+
+namespace content {
+
+class PassiveEventQueueClient {

[Rick Byers, 2016/01/26 19:17:21]

nit: I'm not sure the term "passive event" makes sense.  I've been talking of
"passive event listeners" (a listener function which cannot cancel it's event),
and an optimization to make events uncancelable when there are no non-passive
listeners.  So maybe "uncancelable event" or (as you've done below)
"non-blocking event" is the better term?

Or maybe it makes sense to define "passive event" somewhere.  I'd just want to
articulate the relationship with other uncancelable events.  Eg. are the
touchmove events sent during a scroll "passive events", or are they somehow
different (being uncancelable but not due to passive listeners)?

+ public:
+  virtual void SendPassiveEvent(int routing_id,
+                                const blink::WebInputEvent* event,
+                                const ui::LatencyInfo& latency);
+};
+
+class PassiveEventQueue {
+ public:
+  PassiveEventQueue(int routing_id, PassiveEventQueueClient* client);
+  ~PassiveEventQueue();
+
+  void HandleNonBlockingEvent(const blink::WebInputEvent* event,
+                              const ui::LatencyInfo& latency);
+
+  void EventHandled(blink::WebInputEvent::Type type);
+
+ private:
+  int routing_id_;
+  PassiveEventQueueClient* client_;
+  WebInputEventQueue<MouseWheelEventWithLatencyInfo> wheel_events_;
+  WebInputEventQueue<TouchEventWithLatencyInfo> touch_events_;
+
+  DISALLOW_COPY_AND_ASSIGN(PassiveEventQueue);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_INPUT_WEB_INPUT_EVENT_QUEUE_H_