Use invalidation sets for :lang changes.

third_party/WebKit/Source/core/dom/Element.cpp

Index: third_party/WebKit/Source/core/dom/Element.cpp
diff --git a/third_party/WebKit/Source/core/dom/Element.cpp b/third_party/WebKit/Source/core/dom/Element.cpp
index 0647baada5f00ba90b0589186fce2f144c5431d8..125bbb7a1520b0d3b625b5482da8f7ce553af6e1 100644
--- a/third_party/WebKit/Source/core/dom/Element.cpp
+++ b/third_party/WebKit/Source/core/dom/Element.cpp
@@ -2227,6 +2227,8 @@ void Element::parseAttribute(const QualifiedName& name, const AtomicString&, con
             // Clamp tabindex to the range of 'short' to match Firefox's behavior.
             setTabIndexExplicitly(max(static_cast<int>(std::numeric_limits<short>::min()), std::min(tabindex, static_cast<int>(std::numeric_limits<short>::max()))));
         }
+    } else if (name == XMLNames::langAttr) {
+        pseudoStateChanged(CSSSelector::PseudoLang);
     }
 }