Make ElementShadow::oldestShadowRoot() return a reference

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 3c2dbb90c5f908583efdb5e25bcc3ceee1c2be86..dc5e4011375c263c86a6e7aad72eeb05a1068f9a 100644
--- a/third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp
+++ b/third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp
@@ -421,7 +421,7 @@ static void matchHostRules(const Element& element, ElementRuleCollector& collect
     if (!shadow)
         return;
 
-    for (ShadowRoot* shadowRoot = shadow->oldestShadowRoot(); shadowRoot; shadowRoot = shadowRoot->youngerShadowRoot()) {
+    for (ShadowRoot* shadowRoot = &shadow->oldestShadowRoot(); shadowRoot; shadowRoot = shadowRoot->youngerShadowRoot()) {
         if (!shadowRoot->numberOfStyles())
             continue;
         if (ScopedStyleResolver* resolver = shadowRoot->scopedStyleResolver()) {