Plumb firing passive event listeners.

content/renderer/input/web_input_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_WEB_INPUT_EVENT_QUEUE_H_
+#define CONTENT_RENDERER_INPUT_WEB_INPUT_EVENT_QUEUE_H_
+
+#include <deque>
+
+namespace content {
+
+template <typename T>
+class WebInputEventQueue {

[aelias_OOO_until_Jul13, 2016/01/26 04:50:41]

Hmm, we sure have a lot of queue classes now.  This one is the simplest -- maybe
we should refactor the browser-side ones to make use of this as a primitive. 
Not necessarily for this patch, though.

[dtapuska, 2016/01/26 16:53:15]

Acknowledged.

+ public:
+  enum class State { ITEM_PENDING, ITEM_NOT_PENDING };
+
+  WebInputEventQueue() : state_(State::ITEM_NOT_PENDING) {}
+
+  ~WebInputEventQueue() {
+    if (!queue_.empty())
+      STLDeleteElements(&queue_);
+  }
+
+  // Adds an event to the queue. The event may be coalesced with previously
+  // queued events.
+  void Queue(const T& event) {
+    if (!queue_.empty()) {
+      T* last_event = queue_.back();
+      if (last_event->CanCoalesceWith(event)) {
+        last_event->CoalesceWith(event);
+        return;
+      }
+    }
+    queue_.push_back(new T(event));
+  }
+
+  scoped_ptr<T> Deque() {
+    scoped_ptr<T> result;
+    if (!queue_.empty()) {
+      result.reset(queue_.front());
+      queue_.pop_front();
+    }
+    return result;
+  }
+
+  bool empty() const { return queue_.empty(); }
+
+  size_t size() const { return queue_.size(); }
+
+  void set_state(State state) { state_ = state; }
+
+  State state() const WARN_UNUSED_RESULT { return state_; }
+
+ private:
+  typedef std::deque<T*> EventQueue;

[aelias_OOO_until_Jul13, 2016/01/26 04:50:41]

Please switch to std::deque<scoped_ptr<T>>, that works fine nowadays judging
from https://codereview.chromium.org/1441613002

[dtapuska, 2016/01/26 16:53:15]

Done.

+  EventQueue queue_;
+  State state_;
+
+  DISALLOW_COPY_AND_ASSIGN(WebInputEventQueue);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_INPUT_WEB_INPUT_EVENT_QUEUE_H_