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

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

Index: third_party/WebKit/Source/core/dom/Document.cpp
diff --git a/third_party/WebKit/Source/core/dom/Document.cpp b/third_party/WebKit/Source/core/dom/Document.cpp
index c44b227186644837c5a4a628e8e496940d1075d4..69ee81fdce70d8373b2aa83a2dcc761fe321cb48 100644
--- a/third_party/WebKit/Source/core/dom/Document.cpp
+++ b/third_party/WebKit/Source/core/dom/Document.cpp
@@ -6019,13 +6019,15 @@ static LayoutObject* nearestCommonHoverAncestor(LayoutObject* obj1,
 
 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);
@@ -6034,7 +6036,7 @@ void Document::updateHoverActiveState(const HitTestRequest& request,
 
   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.