Add knowledge about blocking and passive event listeners.

cc/input/event_listener_properties.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 CC_INPUT_EVENT_LISTENER_PROPERTIES_H_
 #define CC_INPUT_EVENT_LISTENER_PROPERTIES_H_
 
 namespace cc {
 
 enum class EventListenerClass { kTouch, kMouseWheel, kNumClasses };
 
-enum class EventListenerProperties { kNone, kPassive, kBlocking, kMax };
+enum class EventListenerProperties {
+  kNone,
+  kPassive,
+  kBlocking,
+  kBlockingAndPassive,
+  kMax
+};
 
 }  // namespace cc
 
 #endif  // CC_INPUT_EVENT_LISTENER_PROPERTIES_H_