Document::updateHoverActiveState only cancel hover and active state when hitting native scrollbar

third_party/WebKit/Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All
  * rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved.
  * (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
@@ skipping 6001 matching lines @@
       if (currObj1 == currObj2)
         return currObj1;
     }
   }
 
   return 0;
 }
 
 void Document::updateHoverActiveState(const HitTestRequest& request,
                                       Element* innerElement,
-                                      bool hitScrollbar) {
+                                      Scrollbar* hitScrollbar) {
   DCHECK(!request.readOnly());
 
-  if (request.active() && m_frame && !hitScrollbar)
+  bool hitNativeScrollbar = hitScrollbar && !hitScrollbar->isCustomScrollbar();

[bokan, 2016/11/23 17:09:51]

Please add a comment here on why custom scrollbars are special (because they
participate in hover activation with the content).

+
+  if (request.active() && m_frame && !hitNativeScrollbar)
     m_frame->eventHandler().notifyElementActivated();
 
-  Element* innerElementInDocument = hitScrollbar ? nullptr : innerElement;
+  Element* innerElementInDocument = hitNativeScrollbar ? nullptr : innerElement;
   while (innerElementInDocument && innerElementInDocument->document() != this) {
     innerElementInDocument->document().updateHoverActiveState(
         request, innerElementInDocument, hitScrollbar);
     innerElementInDocument = innerElementInDocument->document().localOwner();
   }
 
   updateDistribution();
   Element* oldActiveElement = activeHoverElement();
-  if (oldActiveElement && (!request.active() || hitScrollbar)) {
+  if (oldActiveElement && (!request.active() || hitNativeScrollbar)) {
     // The oldActiveElement layoutObject is null, dropped on :active by setting
     // display: none, for instance. We still need to clear the ActiveChain as
     // the mouse is released.
     for (Node* node = oldActiveElement; node;
          node = FlatTreeTraversal::parent(*node)) {
       DCHECK(!node->isTextNode());
       node->setActive(false);
       m_userActionElements.setInActiveChain(node, false);
     }
     setActiveHoverElement(nullptr);
@@ skipping 474 matching lines @@
 }
 
 void showLiveDocumentInstances() {
   WeakDocumentSet& set = liveDocumentSet();
   fprintf(stderr, "There are %u documents currently alive:\n", set.size());
   for (Document* document : set)
     fprintf(stderr, "- Document %p URL: %s\n", document,
             document->url().getString().utf8().data());
 }
 #endif