Generalize the main thread event queue into a common event queue.

content/renderer/input/main_thread_event_queue.cc

Index: content/renderer/input/main_thread_event_queue.cc
diff --git a/content/renderer/input/main_thread_event_queue.cc b/content/renderer/input/main_thread_event_queue.cc
index 6581056c741f3c8ca622af3a1f7ba26c09db127c..824bb39a541ad1bc3b4c6491371ed480247e464a 100644
--- a/content/renderer/input/main_thread_event_queue.cc
+++ b/content/renderer/input/main_thread_event_queue.cc
@@ -3,12 +3,44 @@
 // found in the LICENSE file.
 
 #include "content/renderer/input/main_thread_event_queue.h"
+#include "content/common/input/event_with_latency_info.h"
+#include "content/common/input_messages.h"
 
 namespace content {
 
+EventWithDispatchType::EventWithDispatchType(
+    const blink::WebInputEvent& event,
+    const ui::LatencyInfo& latency,
+    InputEventDispatchType dispatch_type)
+    : ScopedWebInputEventWithLatencyInfo(event, latency),
+      dispatch_type_(dispatch_type) {}
+
+EventWithDispatchType::~EventWithDispatchType() {}
+
+bool EventWithDispatchType::CanCoalesceWith(
+    const EventWithDispatchType& other) const {
+  return other.dispatch_type_ == dispatch_type_ &&
+         ScopedWebInputEventWithLatencyInfo::CanCoalesceWith(other);
+}
+
+void EventWithDispatchType::CoalesceWith(const EventWithDispatchType& other) {
+  // If we are blocking and are coalescing touch, make sure to keep
+  // the touch ids that need to be acked.
+  if (dispatch_type_ == DISPATCH_TYPE_BLOCKING_NOTIFY_MAIN) {
+    // We should only have blocking touch events that need coalescing.
+    DCHECK(blink::WebInputEvent::isTouchEventType(other.event().type));
+    eventsToAck_.push_back(
+        WebInputEventTraits::GetUniqueTouchEventId(other.event()));
+  }
+  ScopedWebInputEventWithLatencyInfo::CoalesceWith(other);
+}
+
 MainThreadEventQueue::MainThreadEventQueue(int routing_id,
                                            MainThreadEventQueueClient* client)
-    : routing_id_(routing_id), client_(client), is_flinging_(false) {}
+    : routing_id_(routing_id),
+      client_(client),
+      is_flinging_(false),
+      sent_notification_to_main_(false) {}
 
 MainThreadEventQueue::~MainThreadEventQueue() {}
 
@@ -29,63 +61,42 @@ bool MainThreadEventQueue::HandleEvent(
       non_blocking ? DISPATCH_TYPE_NON_BLOCKING_NOTIFY_MAIN
                    : DISPATCH_TYPE_BLOCKING_NOTIFY_MAIN;
 
-  if (event->type == blink::WebInputEvent::MouseWheel) {
-    PendingMouseWheelEvent modified_dispatch_type_event =
-        PendingMouseWheelEvent(
-            *static_cast<const blink::WebMouseWheelEvent*>(event), latency,
-            dispatch_type);
+  bool is_wheel = event->type == blink::WebInputEvent::MouseWheel;
+  bool is_touch = blink::WebInputEvent::isTouchEventType(event->type);
+
+  if (is_wheel || is_touch) {
+    std::unique_ptr<EventWithDispatchType> cloned_event(
+        new EventWithDispatchType(*event, latency, dispatch_type));
 
     // Adjust the |dispatchType| on the event since the compositor
     // determined all event listeners are passive.
     if (non_blocking) {
-      modified_dispatch_type_event.event.dispatchType =
-          blink::WebInputEvent::ListenersNonBlockingPassive;
-    }
-
-    if (wheel_events_.state() == WebInputEventQueueState::ITEM_PENDING) {
-      wheel_events_.Queue(modified_dispatch_type_event);
-    } else {
-      if (non_blocking) {
-        wheel_events_.set_state(WebInputEventQueueState::ITEM_PENDING);
-        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_,
-                                       &modified_dispatch_type_event.event,
-                                       latency, original_dispatch_type);
+      if (is_wheel) {
+        static_cast<blink::WebMouseWheelEvent&>(cloned_event->event())
+            .dispatchType = blink::WebInputEvent::ListenersNonBlockingPassive;
+      } else if (is_touch) {
+        static_cast<blink::WebTouchEvent&>(cloned_event->event()).dispatchType =
+            blink::WebInputEvent::ListenersNonBlockingPassive;
       }
     }
-  } else if (blink::WebInputEvent::isTouchEventType(event->type)) {
-    PendingTouchEvent modified_dispatch_type_event =
-        PendingTouchEvent(*static_cast<const blink::WebTouchEvent*>(event),
-                          latency, dispatch_type);
-    modified_dispatch_type_event.event.dispatchedDuringFling = is_flinging_;
 
-    // Adjust the |dispatchType| on the event since the compositor
-    // determined all event listeners are passive.
-    if (non_blocking) {
-      modified_dispatch_type_event.event.dispatchType =
-          blink::WebInputEvent::ListenersNonBlockingPassive;
+    if (is_touch) {
+      static_cast<blink::WebTouchEvent&>(cloned_event->event())
+          .dispatchedDuringFling = is_flinging_;
     }
 
-    if (touch_events_.state() == WebInputEventQueueState::ITEM_PENDING) {
-      touch_events_.Queue(modified_dispatch_type_event);
+    if (sent_notification_to_main_) {
+      events_.Queue(std::move(cloned_event));
     } else {
       if (non_blocking) {
-        touch_events_.set_state(WebInputEventQueueState::ITEM_PENDING);
-        client_->SendEventToMainThread(routing_id_,
-                                       &modified_dispatch_type_event.event,
+        sent_notification_to_main_ = true;
+        client_->SendEventToMainThread(routing_id_, &cloned_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_,
-                                       &modified_dispatch_type_event.event,
+        client_->SendEventToMainThread(routing_id_, &cloned_event->event(),
                                        latency, original_dispatch_type);
       }
     }
@@ -100,39 +111,20 @@ bool MainThreadEventQueue::HandleEvent(
 
 void MainThreadEventQueue::EventHandled(blink::WebInputEvent::Type type,
                                         InputEventAckState ack_result) {
-  if (type == blink::WebInputEvent::MouseWheel) {
-    // There should not be two blocking wheel events in flight.
-    DCHECK(!in_flight_wheel_event_ ||
-           in_flight_wheel_event_->eventsToAck.size() == 0);
-
-    if (!wheel_events_.empty()) {
-      in_flight_wheel_event_ = wheel_events_.Pop();
-      client_->SendEventToMainThread(
-          routing_id_, &in_flight_wheel_event_->event,
-          in_flight_wheel_event_->latency, in_flight_wheel_event_->type);
-    } else {
-      in_flight_wheel_event_.reset();
-      wheel_events_.set_state(WebInputEventQueueState::ITEM_NOT_PENDING);
-    }
-  } else if (blink::WebInputEvent::isTouchEventType(type)) {
-    if (in_flight_touch_event_) {
-      // Send acks for blocking touch events.
-      for (const auto id : in_flight_touch_event_->eventsToAck)
-        client_->SendInputEventAck(routing_id_, type, ack_result, id);
+  if (in_flight_event_) {
+    // Send acks for blocking touch events.
+    for (const auto id : in_flight_event_->eventsToAck())
+      client_->SendInputEventAck(routing_id_, type, ack_result, id);
     }
-
-    if (!touch_events_.empty()) {
-      in_flight_touch_event_ = touch_events_.Pop();
-      client_->SendEventToMainThread(
-          routing_id_, &in_flight_touch_event_->event,
-          in_flight_touch_event_->latency, in_flight_touch_event_->type);
+    if (!events_.empty()) {
+      in_flight_event_ = events_.Pop();
+      client_->SendEventToMainThread(routing_id_, &in_flight_event_->event(),
+                                     in_flight_event_->latencyInfo(),
+                                     in_flight_event_->dispatchType());
     } else {
-      in_flight_touch_event_.reset();
-      touch_events_.set_state(WebInputEventQueueState::ITEM_NOT_PENDING);
+      in_flight_event_.reset();
+      sent_notification_to_main_ = false;
     }
-  } else {
-    NOTREACHED() << "Invalid passive event type";
-  }
 }
 
 }  // namespace content