Make event-targeting asynchronous in window server.

services/ui/ws/window_manager_state.h

Index: services/ui/ws/window_manager_state.h
diff --git a/services/ui/ws/window_manager_state.h b/services/ui/ws/window_manager_state.h
index ce897244a81ee49e82e48e4f17faf0a33184868e..d801681abb0d2fad9cdcd5a411f181dd232848ff 100644
--- a/services/ui/ws/window_manager_state.h
+++ b/services/ui/ws/window_manager_state.h
@@ -153,13 +153,13 @@ class WindowManagerState : public EventDispatcherDelegate,
   };
 
   // Tracks state associated with an event being dispatched to a client.
-  struct InFlightEventDetails {
-    InFlightEventDetails(WindowManagerState* window_manager_state,
-                         WindowTree* tree,
-                         int64_t display_id,
-                         const Event& event,
-                         EventDispatchPhase phase);
-    ~InFlightEventDetails();
+  struct InFlightEventDispatchDetails {
+    InFlightEventDispatchDetails(WindowManagerState* window_manager_state,
+                                 WindowTree* tree,
+                                 int64_t display_id,
+                                 const Event& event,
+                                 EventDispatchPhase phase);
+    ~InFlightEventDispatchDetails();
 
     base::OneShotTimer timer;
     WindowTree* tree;
@@ -213,11 +213,6 @@ class WindowManagerState : public EventDispatcherDelegate,
                   std::unique_ptr<ProcessedEventTarget> processed_event_target,
                   int64_t display_id);
 
-  // Processes the next valid event in |event_queue_|. If the event has already
-  // been processed it is dispatched, otherwise the event is passed to the
-  // EventDispatcher for processing.
-  void ProcessNextEventFromQueue();
-
   // Dispatches the event to the appropriate client and starts the ack timer.
   void DispatchInputEventToWindowImpl(ServerWindow* target,
                                       ClientSpecificId client_id,
@@ -256,6 +251,10 @@ class WindowManagerState : public EventDispatcherDelegate,
                                   ClientSpecificId client_id,
                                   const Event& event,
                                   Accelerator* accelerator) override;
+  // Processes the next valid event in |event_queue_|. If the event has already
+  // been processed it is dispatched, otherwise the event is passed to the
+  // EventDispatcher for processing.
+  void ProcessNextEventFromQueue() override;
   ClientSpecificId GetEventTargetClientId(const ServerWindow* window,
                                           bool in_nonclient_area) override;
   ServerWindow* GetRootWindowContaining(gfx::Point* location) override;
@@ -272,13 +271,16 @@ class WindowManagerState : public EventDispatcherDelegate,
   bool got_frame_decoration_values_ = false;
   mojom::FrameDecorationValuesPtr frame_decoration_values_;
 
+  // Events can go into this queue if there's a hit-test in flight in
+  // EventDispatcher or if we are actively dispatching an event.
   std::queue<std::unique_ptr<QueuedEvent>> event_queue_;
 
   std::vector<DebugAccelerator> debug_accelerators_;
 
   // If non-null we're actively waiting for a response from a client for an
   // event.
-  std::unique_ptr<InFlightEventDetails> in_flight_event_details_;
+  std::unique_ptr<InFlightEventDispatchDetails>
+      in_flight_event_dispatch_details_;
 
   EventDispatcher event_dispatcher_;