Update hover states when dragging the mouse into an element

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 49fc092b98dac85b94151d33315c4fa83057bbfb..16f0c9d5021decdcfe58eaf2664afa5f2514c4f9 100644
--- a/third_party/WebKit/Source/core/dom/Document.cpp
+++ b/third_party/WebKit/Source/core/dom/Document.cpp
@@ -6489,7 +6489,7 @@ void Document::UpdateHoverActiveState(const HitTestRequest& request,
   bool allow_active_changes = !old_active_element && ActiveHoverElement();
 
   // If the mouse is down and if this is a mouse move event, we want to restrict
-  // changes in :hover/:active to only apply to elements that are in the :active
+  // changes in :active to only apply to elements that are in the :active
   // chain that we froze at the time the mouse went down.
   bool must_be_in_active_chain = request.Active() && request.Move();
 
@@ -6516,7 +6516,8 @@ void Document::UpdateHoverActiveState(const HitTestRequest& request,
   }
 
   HeapVector<Member<Element>, 32> elements_to_remove_from_chain;
-  HeapVector<Member<Element>, 32> elements_to_add_to_chain;
+  HeapVector<Member<Element>, 32> elements_to_add_to_active_chain;
+  HeapVector<Member<Element>, 32> elements_to_add_to_hover_chain;
 
   if (old_hover_element != new_hover_element) {
     // The old hover path only needs to be cleared up to (and not including) the
@@ -6532,8 +6533,7 @@ void Document::UpdateHoverActiveState(const HitTestRequest& request,
     if (old_hover_element && old_hover_element->isConnected()) {
       for (Element* curr = old_hover_element; curr && curr != ancestor_element;
            curr = FlatTreeTraversal::ParentElement(*curr)) {
-        if (!must_be_in_active_chain || curr->InActiveChain())
-          elements_to_remove_from_chain.push_back(curr);
+        elements_to_remove_from_chain.push_back(curr);
       }
     }
   }
@@ -6541,8 +6541,9 @@ void Document::UpdateHoverActiveState(const HitTestRequest& request,
   // Now set the hover state for our new object up to the root.
   for (Element* curr = new_hover_element; curr;
        curr = FlatTreeTraversal::ParentElement(*curr)) {
+    elements_to_add_to_hover_chain.push_back(curr);

[Navid Zolghadr, 2017/07/04 17:51:59]

Do we need a check like old_hover_element != new_hover_element here? Basically
if they are the same we don't want to change any hover and this array should be
empty similar to the elements_to_remove_from_chain array?

     if (!must_be_in_active_chain || curr->InActiveChain())
-      elements_to_add_to_chain.push_back(curr);
+      elements_to_add_to_active_chain.push_back(curr);
   }
 
   if (allow_hover_changes) {
@@ -6550,14 +6551,17 @@ void Document::UpdateHoverActiveState(const HitTestRequest& request,
       element->SetHovered(false);
   }
 
+  // Elements past the common ancestor do not change hover state, but might
+  // change active state.
+  for (Element* element : elements_to_add_to_active_chain) {
+    if (allow_active_changes)
+      element->SetActive(true);
+  }
+
   bool saw_common_ancestor = false;
-  for (Element* element : elements_to_add_to_chain) {
-    // Elements past the common ancestor do not change hover state, but might
-    // change active state.
+  for (Element* element : elements_to_add_to_hover_chain) {
     if (element == ancestor_element)
       saw_common_ancestor = true;
-    if (allow_active_changes)
-      element->SetActive(true);
     if (allow_hover_changes &&
         (!saw_common_ancestor || element == hover_element_))
       element->SetHovered(true);