Migrate wheel events to EventHandlerRegistry

Source/core/frame/EventHandlerRegistry.h

 // Copyright 2014 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 EventHandlerRegistry_h
 #define EventHandlerRegistry_h
 
 #include "core/events/Event.h"
 #include "core/frame/FrameHost.h"
 #include "wtf/HashCountedSet.h"
 
 namespace WebCore {
 
 typedef HashCountedSet<EventTarget*> EventTargetSet;
 
 // Registry for keeping track of event handlers. Note that only handlers on
 // documents that can be rendered or can receive input (i.e., are attached to a
 // FrameHost) are registered here.
 class EventHandlerRegistry FINAL : public NoBaseWillBeGarbageCollectedFinalized<EventHandlerRegistry> {
 public:
     explicit EventHandlerRegistry(FrameHost&);
     virtual ~EventHandlerRegistry();
 
     // Supported event handler classes. Note that each one may correspond to
     // multiple event types.
     enum EventHandlerClass {
         ScrollEvent,
+        WheelEvent,
 #if ASSERT_ENABLED
         // Additional event categories for verifying handler tracking logic.
         EventsForTesting,
 #endif
         EventHandlerClassCount, // Must be the last entry.
     };
 
     // Returns true if the FrameHost has event handlers of the specified class.
     bool hasEventHandlers(EventHandlerClass) const;
 
     // Returns a set of EventTargets which have registered handlers of the given class.
     const EventTargetSet* eventHandlerTargets(EventHandlerClass) const;
 
+    // Returns the number of external event handlers for a given class.
+    // External handlers are not included in |eventHandlerTargets|.
+    unsigned externalEventHandlerCount(EventHandlerClass) const;
+
     // Registration and management of event handlers attached to EventTargets.
     void didAddEventHandler(EventTarget&, const AtomicString& eventType);
     void didAddEventHandler(EventTarget&, EventHandlerClass);
     void didRemoveEventHandler(EventTarget&, const AtomicString& eventType);
     void didRemoveEventHandler(EventTarget&, EventHandlerClass);
     void didRemoveAllEventHandlers(EventTarget&);
     void didMoveIntoFrameHost(EventTarget&);
     void didMoveOutOfFrameHost(EventTarget&);
 
     // Either |documentDetached| or |didMoveOutOfFrameHost| must be called
     // whenever the FrameHost that is associated with a registered event target
     // changes. This ensures the registry does not end up with stale references
     // to handlers that are no longer related to it.
     void documentDetached(Document&);
 
+    // Registration of event handlers attached to non-DOM objects.
+    void didAddExternalEventHandler(const AtomicString& eventType);
+    void didRemoveExternalEventHandler(const AtomicString& eventType);
+
     void trace(Visitor*);
     void clearWeakMembers(Visitor*);
 
 private:
     enum ChangeOperation {
         Add, // Add a new event handler.
         Remove, // Remove an existing event handler.
         RemoveAll // Remove any and all existing event handlers for a given target.
     };
 
     // Returns true if |eventType| belongs to a class this registry tracks.
     static bool eventTypeToClass(const AtomicString& eventType, EventHandlerClass* result);
 
     // Returns true if the operation actually added a new target or completely
     // removed an existing one.
     bool updateEventHandlerTargets(ChangeOperation, EventHandlerClass, EventTarget*);
 
     // Called on the EventHandlerRegistry of the root Document to notify
     // clients when we have added the first handler or removed the last one for
     // a given event class. |hasActiveHandlers| can be used to distinguish
     // between the two cases.
     void notifyHasHandlersChanged(EventHandlerClass, bool hasActiveHandlers);
 
     // Record a change operation to a given event handler class and notify any
     // parent registry and other clients accordingly.
     void updateEventHandlerOfType(ChangeOperation, const AtomicString& eventType, EventTarget*);
 
+    void updateExternalHandlerCount(ChangeOperation, EventHandlerClass);
     void updateEventHandlerInternal(ChangeOperation, EventHandlerClass, EventTarget*);
 
     void updateAllEventHandlers(ChangeOperation, EventTarget&);
 
     void checkConsistency() const;
 
     FrameHost& m_frameHost;
-    EventTargetSet m_targets[EventHandlerClassCount];
+
+    struct HandlerState {
+        HandlerState();
+        ~HandlerState();
+
+        EventTargetSet targets;
+        // External handlers are not included in |targets|.
+        unsigned externalHandlerCount;
+    };
+
+    HandlerState m_handlers[EventHandlerClassCount];
 };
 
 } // namespace WebCore
 
 #endif // EventHandlerRegistry_h