Plumb firing passive event listeners.

content/renderer/input/non_blocking_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_NON_BLOCKING_EVENT_QUEUE_H_
+#define CONTENT_RENDERER_INPUT_NON_BLOCKING_EVENT_QUEUE_H_
+
+#include <deque>
+#include "content/common/content_export.h"
+#include "content/common/input/event_with_latency_info.h"
+#include "content/common/input/web_input_event_queue.h"
+#include "third_party/WebKit/public/web/WebInputEvent.h"
+#include "ui/events/latency_info.h"
+
+namespace content {
+
+class CONTENT_EXPORT NonBlockingEventQueueClient {
+ public:
+  // Send an |event| that was previously queued (possibly
+  // coalesced with another event) to the |routing_id|'s
+  // channel. Implementors must implement this callback.
+  virtual void SendNonBlockingEvent(int routing_id,
+                                    const blink::WebInputEvent* event,
+                                    const ui::LatencyInfo& latency) = 0;
+};
+
+// NonBlockingEventQueue implements a series of queues (one touch
+// and one mouse wheel) for events that need to be queued between
+// the compositor and main threads. When a non-blocking event is sent
+// from the compositor to main it can either be sent directly if no
+// outstanding events of that type are in flight; or it needs to
+// wait in a queue until the main thread has finished processing
+// the in-flight event. This class tracks the state and queues
+// for the event types. Methods on this class should only be called
+// from the compositor thread.
+//
+class CONTENT_EXPORT NonBlockingEventQueue {
+ public:
+  NonBlockingEventQueue(int routing_id, NonBlockingEventQueueClient* client);
+  ~NonBlockingEventQueue();
+
+  // Called once compositor has handled |event| and indicated that it is
+  // a non-blocking event to be queued to the main thread.
+  void HandleEvent(const blink::WebInputEvent* event,
+                   const ui::LatencyInfo& latency);
+
+  // Call once main thread has handled outstanding |type| event in flight.
+  void EventHandled(blink::WebInputEvent::Type type);
+
+ private:
+  friend class NonBlockingEventQueueTest;
+  int routing_id_;
+  NonBlockingEventQueueClient* client_;
+  WebInputEventQueue<MouseWheelEventWithLatencyInfo> wheel_events_;
+  WebInputEventQueue<TouchEventWithLatencyInfo> touch_events_;
+
+  DISALLOW_COPY_AND_ASSIGN(NonBlockingEventQueue);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_INPUT_NON_BLOCKING_EVENT_QUEUE_H_