Avoid unnecessary invalidation scheduling.

third_party/WebKit/Source/core/css/invalidation/StyleInvalidator.cpp

Index: third_party/WebKit/Source/core/css/invalidation/StyleInvalidator.cpp
diff --git a/third_party/WebKit/Source/core/css/invalidation/StyleInvalidator.cpp b/third_party/WebKit/Source/core/css/invalidation/StyleInvalidator.cpp
index c5ac9ea098c3af67161eeb86b1aa5df1ac5c13a1..962a8ae9cd6b96c465481addd67e98256f9fa8a3 100644
--- a/third_party/WebKit/Source/core/css/invalidation/StyleInvalidator.cpp
+++ b/third_party/WebKit/Source/core/css/invalidation/StyleInvalidator.cpp
@@ -60,15 +60,18 @@ void StyleInvalidator::scheduleInvalidationSetsForElement(const InvalidationList
             requiresDescendantInvalidation = true;
     }
 
-    if (invalidationLists.siblings.isEmpty() && !requiresDescendantInvalidation)
+    if (!requiresDescendantInvalidation && (invalidationLists.siblings.isEmpty() || !element.nextSibling()))
         return;
 
     element.setNeedsStyleInvalidation();
+
     PendingInvalidations& pendingInvalidations = ensurePendingInvalidations(element);
-    for (auto& invalidationSet : invalidationLists.siblings) {
-        if (pendingInvalidations.siblings().contains(invalidationSet))
-            continue;
-        pendingInvalidations.siblings().append(invalidationSet);
+    if (element.nextSibling()) {
+        for (auto& invalidationSet : invalidationLists.siblings) {
+            if (pendingInvalidations.siblings().contains(invalidationSet))
+                continue;
+            pendingInvalidations.siblings().append(invalidationSet);
+        }
     }
 
     if (!requiresDescendantInvalidation)