Bug 1460368. Remove now-unused nsContentUtils::GetClosestNonNativeAnonymousAncestor. r=heycam

This was used in the non-stylo style system, but that's all gone now.

dom/base/nsContentUtils.cpp

@@ -10496,19 +10496,6 @@ nsContentUtils::ShouldBlockReservedKeys(WidgetKeyboardEvent* aKeyEvent)
   return false;
 }
 
-/* static */ Element*
-nsContentUtils::GetClosestNonNativeAnonymousAncestor(Element* aElement)
-{
-  MOZ_ASSERT(aElement);
-  MOZ_ASSERT(aElement->IsNativeAnonymous());
-
-  Element* e = aElement;
-  while (e && e->IsNativeAnonymous()) {
-    e = e->GetParentElement();
-  }
-  return e;
-}
-
 /**
  * Checks whether the given type is a supported document type for
  * loading within the nsObjectLoadingContent specified by aContent.

dom/base/nsContentUtils.h

@@ -3120,12 +3120,6 @@ public:
    */
   static bool ShouldBlockReservedKeys(mozilla::WidgetKeyboardEvent* aKeyEvent);
 
-  /**
-   * Walks up the tree from aElement until it finds an element that is
-   * not native anonymous content.  aElement must be NAC itself.
-   */
-  static Element* GetClosestNonNativeAnonymousAncestor(Element* aElement);
-
   /**
    * Returns the nsIPluginTag for the plugin we should try to use for a given
    * MIME type.