Track scroll event handlers in nested documents

Source/core/dom/EventHandlerRegistry.cpp

Index: Source/core/dom/EventHandlerRegistry.cpp
diff --git a/Source/core/dom/EventHandlerRegistry.cpp b/Source/core/dom/EventHandlerRegistry.cpp
index b72b465ffaadc0a31187c14559227570e38b81e7..d7ce9523535ef5d2c2606d421bece0585ef0bbd8 100644
--- a/Source/core/dom/EventHandlerRegistry.cpp
+++ b/Source/core/dom/EventHandlerRegistry.cpp
@@ -17,6 +17,25 @@
 
 namespace WebCore {
 
+EventHandlerRegistry::DocumentObserver::DocumentObserver(Document& document)
+    : ActiveDOMObject(&document)
+{
+}
+
+EventHandlerRegistry::DocumentObserver::~DocumentObserver()
+{
+}
+
+void EventHandlerRegistry::DocumentObserver::stop()
+{
+    Document* document = static_cast<Document*>(lifecycleContext());
+    Document* parentDocument = document->parentDocument();
+    if (!parentDocument)
+        return;
+    EventHandlerRegistry* parentRegistry = EventHandlerRegistry::from(*parentDocument);
+    parentRegistry->didRemoveAllEventHandlers(*document);
+}
+
 EventHandlerRegistry::HandlerState::HandlerState()
 {
 }
@@ -27,7 +46,9 @@ EventHandlerRegistry::HandlerState::~HandlerState()
 
 EventHandlerRegistry::EventHandlerRegistry(Document& document)
     : m_document(document)
+    , m_documentObserver(DocumentObserver(document))
 {
+    m_documentObserver.suspendIfNeeded();
 }
 
 EventHandlerRegistry::~EventHandlerRegistry()
@@ -75,8 +96,12 @@ bool EventHandlerRegistry::updateEventHandlerTargets(ChangeOperation op, EventHa
     EventTargetSet* targets = m_eventHandlers[handlerClass].targets.get();
     if (op == Add) {
 #if ASSERT_ENABLED
-        if (Node* node = target->toNode())
-            ASSERT(&node->document() == &m_document);
+        if (Node* node = target->toNode()) {
+            // The node should either be in the document, or be the Document node of a child
+            // of the document.
+            ASSERT(&node->document() == &m_document
+                || (node->isDocumentNode() && toDocument(node)->parentDocument() == &m_document));
+        }
 #endif // ASSERT_ENABLED
 
         if (!targets) {
@@ -86,6 +111,11 @@ bool EventHandlerRegistry::updateEventHandlerTargets(ChangeOperation op, EventHa
 
         if (!targets->add(target).isNewEntry) {
             // Just incremented refcount, no real change.
+#if ASSERT_ENABLED
+            // If this is a child document node, then the count should never go above 1.
+            if (Node* node = target->toNode())
+                ASSERT(!node->isDocumentNode() || &node->document() == &m_document);
+#endif // ASSERT_ENABLED
             return false;
         }
     } else {
@@ -112,20 +142,28 @@ bool EventHandlerRegistry::updateEventHandlerTargets(ChangeOperation op, EventHa
 
 void EventHandlerRegistry::updateEventHandlerInternal(ChangeOperation op, EventHandlerClass handlerClass, EventTarget* target)
 {
-    // After the document has stopped, all updates become no-ops.
-    if (!m_document.isActive()) {
-        return;
-    }
+    // Notify our parent registry if we added the first or removed the last handler.
+    for (Document* document = &m_document; document; document = document->parentDocument()) {
+        // After the document has stopped, all updates become no-ops.
+        if (!document->isActive()) {
+            return;
+        }
+        EventHandlerRegistry* registry = EventHandlerRegistry::from(*document);
 
-    bool hadHandlers = hasEventHandlers(handlerClass);
-    updateEventHandlerTargets(op, handlerClass, target);
-    bool hasHandlers = hasEventHandlers(handlerClass);
+        bool hadHandlers = registry->hasEventHandlers(handlerClass);
+        registry->updateEventHandlerTargets(op, handlerClass, target);
+        bool hasHandlers = registry->hasEventHandlers(handlerClass);
 
-    // Notify the parent document's registry if we added the first or removed
-    // the last handler.
-    if (hadHandlers != hasHandlers && !m_document.parentDocument()) {
-        // This is the root registry; notify clients accordingly.
-        notifyHasHandlersChanged(handlerClass, hasHandlers);
+        if (hadHandlers == hasHandlers) {
+            break;
+        }
+        if (!document->parentDocument()) {
+            // This is the root registry; notify clients accordingly.
+            registry->notifyHasHandlersChanged(handlerClass, hasHandlers);
+        } else {
+            // Report change to parent with our Document as the target.
+            target = document;
+        }
     }
 }