--- a/accessible/base/nsAccCache.h
+++ b/accessible/base/nsAccCache.h
@@ -8,24 +8,26 @@
 
 #include "xpcAccessibleDocument.h"
 
 ////////////////////////////////////////////////////////////////////////////////
 // Accessible cache utils
 ////////////////////////////////////////////////////////////////////////////////
 
 template <class T>
-static PLDHashOperator
-UnbindCacheEntryFromDocument(const void* aKey, RefPtr<T>& aAccessible,
-                             void* aUserArg)
+void
+UnbindCacheEntriesFromDocument(
+  nsRefPtrHashtable<nsPtrHashKey<const void>, T>& aCache)
 {
-  MOZ_ASSERT(aAccessible && !aAccessible->IsDefunct());
-  aAccessible->Document()->UnbindFromDocument(aAccessible);
-
-  return PL_DHASH_REMOVE;
+  for (auto iter = aCache.Iter(); !iter.Done(); iter.Next()) {
+    T* accessible = iter.Data();
+    MOZ_ASSERT(accessible && !accessible->IsDefunct());
+    accessible->Document()->UnbindFromDocument(accessible);
+    iter.Remove();
+  }
 }
 
 /**
  * Clear the cache and shutdown the accessibles.
  */
 template <class T>
 static void
 ClearCache(nsRefPtrHashtable<nsPtrHashKey<const void>, T>& aCache)

--- a/accessible/xul/XULTreeAccessible.cpp
+++ b/accessible/xul/XULTreeAccessible.cpp
@@ -140,18 +140,19 @@ XULTreeAccessible::Value(nsString& aValu
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // XULTreeAccessible: Accessible implementation
 
 void
 XULTreeAccessible::Shutdown()
 {
-  if (!mDoc->IsDefunct())
-    mAccessibleCache.Enumerate(UnbindCacheEntryFromDocument<Accessible>, nullptr);
+  if (!mDoc->IsDefunct()) {
+    UnbindCacheEntriesFromDocument(mAccessibleCache);
+  }
 
   mTree = nullptr;
   mTreeView = nullptr;
 
   AccessibleWrap::Shutdown();
 }
 
 role
@@ -545,18 +546,17 @@ XULTreeAccessible::GetTreeItemAccessible
 
 void
 XULTreeAccessible::InvalidateCache(int32_t aRow, int32_t aCount)
 {
   if (IsDefunct())
     return;
 
   if (!mTreeView) {
-    mAccessibleCache.Enumerate(UnbindCacheEntryFromDocument<Accessible>,
-                               nullptr);
+    UnbindCacheEntriesFromDocument(mAccessibleCache);
     return;
   }
 
   // Do not invalidate the cache if rows have been inserted.
   if (aCount > 0)
     return;
 
   DocAccessible* document = Document();
@@ -604,18 +604,17 @@ XULTreeAccessible::InvalidateCache(int32
 void
 XULTreeAccessible::TreeViewInvalidated(int32_t aStartRow, int32_t aEndRow,
                                        int32_t aStartCol, int32_t aEndCol)
 {
   if (IsDefunct())
     return;
 
   if (!mTreeView) {
-    mAccessibleCache.Enumerate(UnbindCacheEntryFromDocument<Accessible>,
-                               nullptr);
+    UnbindCacheEntriesFromDocument(mAccessibleCache);
     return;
   }
 
   int32_t endRow = aEndRow;
 
   nsresult rv;
   if (endRow == -1) {
     int32_t rowCount = 0;
@@ -664,35 +663,34 @@ XULTreeAccessible::TreeViewChanged(nsITr
 
   // Fire reorder event on tree accessible on accessible tree (do not fire
   // show/hide events on tree items because it can be expensive to fire them for
   // each tree item.
   RefPtr<AccReorderEvent> reorderEvent = new AccReorderEvent(this);
   Document()->FireDelayedEvent(reorderEvent);
 
   // Clear cache.
-  mAccessibleCache.Enumerate(UnbindCacheEntryFromDocument<Accessible>,
-                             nullptr);
+  UnbindCacheEntriesFromDocument(mAccessibleCache);
 
   mTreeView = aView;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // XULTreeAccessible: protected implementation
 
 already_AddRefed<Accessible>
 XULTreeAccessible::CreateTreeItemAccessible(int32_t aRow) const
 {
   RefPtr<Accessible> accessible =
     new XULTreeItemAccessible(mContent, mDoc, const_cast<XULTreeAccessible*>(this),
                               mTree, mTreeView, aRow);
 
   return accessible.forget();
 }
-                             
+
 ////////////////////////////////////////////////////////////////////////////////
 // XULTreeItemAccessibleBase
 ////////////////////////////////////////////////////////////////////////////////
 
 XULTreeItemAccessibleBase::
   XULTreeItemAccessibleBase(nsIContent* aContent, DocAccessible* aDoc,
                             Accessible* aParent, nsITreeBoxObject* aTree,
                             nsITreeView* aTreeView, int32_t aRow) :

--- a/accessible/xul/XULTreeGridAccessible.cpp
+++ b/accessible/xul/XULTreeGridAccessible.cpp
@@ -272,18 +272,17 @@ NS_IMPL_RELEASE_INHERITED(XULTreeGridRow
 
 ////////////////////////////////////////////////////////////////////////////////
 // XULTreeGridRowAccessible: Accessible implementation
 
 void
 XULTreeGridRowAccessible::Shutdown()
 {
   if (!mDoc->IsDefunct()) {
-    mAccessibleCache.Enumerate(UnbindCacheEntryFromDocument<XULTreeGridCellAccessible>,
-                               nullptr);
+    UnbindCacheEntriesFromDocument(mAccessibleCache);
   }
 
   XULTreeItemAccessibleBase::Shutdown();
 }
 
 role
 XULTreeGridRowAccessible::NativeRole()
 {