Replace style sharing cousin list search with LRU

Source/core/testing/Internals.cpp

Index: Source/core/testing/Internals.cpp
diff --git a/Source/core/testing/Internals.cpp b/Source/core/testing/Internals.cpp
index c10066422bad56026b9e95e32f9c05d96b0742e7..b1c6a504c7137ef91641debb548f692567219c8c 100644
--- a/Source/core/testing/Internals.cpp
+++ b/Source/core/testing/Internals.cpp
@@ -1542,11 +1542,17 @@ void Internals::toggleOverwriteModeEnabled(Document* document, ExceptionState&)
 
 unsigned Internals::numberOfLiveNodes() const
 {
+    if (StyleResolver* resolver = contextDocument()->styleResolverIfExists())
+        resolver->clearStyleSharingList();
+
     return InspectorCounters::counterValue(InspectorCounters::NodeCounter);
 }
 
 unsigned Internals::numberOfLiveDocuments() const
 {
+    if (StyleResolver* resolver = contextDocument()->styleResolverIfExists())
+        resolver->clearStyleSharingList();
+
     return InspectorCounters::counterValue(InspectorCounters::DocumentCounter);
 }
 
@@ -1813,6 +1819,11 @@ void Internals::garbageCollectDocumentResources(Document* document, ExceptionSta
         return;
     }
 
+    if (StyleResolver* resolver = contextDocument()->styleResolverIfExists())
+        resolver->clearStyleSharingList();
+    if (StyleResolver* resolver = document->styleResolverIfExists())
+        resolver->clearStyleSharingList();
+
     ResourceFetcher* fetcher = document->fetcher();
     if (!fetcher)
         return;