No need to look up Document from Element.

third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp

Index: third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp
diff --git a/third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp b/third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp
index 3cee9f558ddf9765e536d184c327ffd0ce364493..e1fd99fdcbae06978f25fff588d3640d13b57301 100644
--- a/third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp
+++ b/third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp
@@ -524,7 +524,7 @@ void StyleResolver::matchScopedRules(const Element& element, ElementRuleCollecto
 
 void StyleResolver::matchAuthorRules(const Element& element, ElementRuleCollector& collector)
 {
-    if (element.document().styleEngine().shadowCascadeOrder() != ShadowCascadeOrder::ShadowCascadeV1) {
+    if (document().styleEngine().shadowCascadeOrder() != ShadowCascadeOrder::ShadowCascadeV1) {
         matchAuthorRulesV0(element, collector);
         return;
     }
@@ -609,7 +609,7 @@ void StyleResolver::matchAllRules(StyleResolverState& state, ElementRuleCollecto
 
     if (state.element()->isStyledElement()) {
         // For Shadow DOM V1, inline style is already collected in matchScopedRules().
-        if (state.element()->document().styleEngine().shadowCascadeOrder() != ShadowCascadeOrder::ShadowCascadeV1 && state.element()->inlineStyle()) {
+        if (document().styleEngine().shadowCascadeOrder() != ShadowCascadeOrder::ShadowCascadeV1 && state.element()->inlineStyle()) {
             // Inline style is immutable as long as there is no CSSOM wrapper.
             bool isInlineStyleCacheable = !state.element()->inlineStyle()->isMutable();
             collector.addElementStyleProperties(state.element()->inlineStyle(), isInlineStyleCacheable);