--- a/dom/html/HTMLBRElement.cpp
+++ b/dom/html/HTMLBRElement.cpp
@@ -48,29 +48,27 @@ HTMLBRElement::ParseAttribute(int32_t aN
   }
 
   return nsGenericHTMLElement::ParseAttribute(aNamespaceID, aAttribute, aValue,
                                               aResult);
 }
 
 void
 HTMLBRElement::MapAttributesIntoRule(const nsMappedAttributes* aAttributes,
-                                     GenericSpecifiedValues* aGenericData)
+                                     GenericSpecifiedValues* aData)
 {
-  nsRuleData* aData = aGenericData->AsRuleData();
-  if (aData->mSIDs & NS_STYLE_INHERIT_BIT(Display)) {
-    nsCSSValue* clear = aData->ValueForClear();
-    if (clear->GetUnit() == eCSSUnit_Null) {
+  if (aData->ShouldComputeStyleStruct(NS_STYLE_INHERIT_BIT(Display))) {
+    if (!aData->PropertyIsSet(eCSSProperty_clear)) {
       const nsAttrValue* value = aAttributes->GetAttr(nsGkAtoms::clear);
       if (value && value->Type() == nsAttrValue::eEnum)
-        clear->SetIntValue(value->GetEnumValue(), eCSSUnit_Enumerated);
+        aData->SetKeywordValue(eCSSProperty_clear, value->GetEnumValue());
     }
   }
 
-  nsGenericHTMLElement::MapCommonAttributesInto(aAttributes, aGenericData);
+  nsGenericHTMLElement::MapCommonAttributesInto(aAttributes, aData);
 }
 
 NS_IMETHODIMP_(bool)
 HTMLBRElement::IsAttributeMapped(const nsIAtom* aAttribute) const
 {
   static const MappedAttributeEntry attributes[] = {
     { &nsGkAtoms::clear },
     { nullptr }