Revert of Collect active stylesheets and and apply asynchronously.

third_party/WebKit/Source/core/css/StyleSheetContents.cpp

Index: third_party/WebKit/Source/core/css/StyleSheetContents.cpp
diff --git a/third_party/WebKit/Source/core/css/StyleSheetContents.cpp b/third_party/WebKit/Source/core/css/StyleSheetContents.cpp
index 7dc7792ec83c2499842949c2d322ef499777b200..b24baaa1190fa6f8900c75172e926a3d657739e4 100644
--- a/third_party/WebKit/Source/core/css/StyleSheetContents.cpp
+++ b/third_party/WebKit/Source/core/css/StyleSheetContents.cpp
@@ -617,14 +617,10 @@
   return *m_ruleSet.get();
 }
 
-static void setNeedsActiveStyleUpdateForClients(
-    HeapHashSet<WeakMember<CSSStyleSheet>>& clients) {
+static void clearResolvers(HeapHashSet<WeakMember<CSSStyleSheet>>& clients) {
   for (const auto& sheet : clients) {
-    Document* document = sheet->ownerDocument();
-    Node* node = sheet->ownerNode();
-    if (!document || !node || !node->isConnected())
-      continue;
-    document->styleEngine().setNeedsActiveStyleUpdate(node->treeScope());
+    if (Document* document = sheet->ownerDocument())
+      document->styleEngine().clearResolver();
   }
 }
 
@@ -632,12 +628,18 @@
   if (StyleSheetContents* parentSheet = parentStyleSheet())
     parentSheet->clearRuleSet();
 
+  // Don't want to clear the StyleResolver if the RuleSet hasn't been created
+  // since we only clear the StyleResolver so that it's members are properly
+  // updated in ScopedStyleResolver::addRulesFromSheet.
   if (!m_ruleSet)
     return;
 
+  // Clearing the ruleSet means we need to recreate the styleResolver data
+  // structures. See the StyleResolver calls in
+  // ScopedStyleResolver::addRulesFromSheet.
+  clearResolvers(m_loadingClients);
+  clearResolvers(m_completedClients);
   m_ruleSet.clear();
-  setNeedsActiveStyleUpdateForClients(m_loadingClients);
-  setNeedsActiveStyleUpdateForClients(m_completedClients);
 }
 
 static void removeFontFaceRules(HeapHashSet<WeakMember<CSSStyleSheet>>& clients,