Revert of Collect active stylesheets and and apply asynchronously.

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

Index: third_party/WebKit/Source/core/dom/ShadowTreeStyleSheetCollection.cpp
diff --git a/third_party/WebKit/Source/core/dom/ShadowTreeStyleSheetCollection.cpp b/third_party/WebKit/Source/core/dom/ShadowTreeStyleSheetCollection.cpp
index 7f735dd5d9bb6c537f8375d32dcbf24e20def2b5..29dad5ffed2e06abdc62cbe4e4216c7898605a2f 100644
--- a/third_party/WebKit/Source/core/dom/ShadowTreeStyleSheetCollection.cpp
+++ b/third_party/WebKit/Source/core/dom/ShadowTreeStyleSheetCollection.cpp
@@ -47,6 +47,7 @@
     : TreeScopeStyleSheetCollection(shadowRoot) {}
 
 void ShadowTreeStyleSheetCollection::collectStyleSheets(
+    StyleEngine& engine,
     StyleSheetCollection& collection) {
   for (Node* n : m_styleSheetCandidateNodes) {
     StyleSheetCandidate candidate(*n);
@@ -57,19 +58,46 @@
       continue;
 
     collection.appendSheetForList(sheet);
-    if (candidate.canBeActivated(nullAtom)) {
-      CSSStyleSheet* cssSheet = toCSSStyleSheet(sheet);
-      collection.appendActiveStyleSheet(std::make_pair(
-          cssSheet, document().styleEngine().ruleSetForSheet(*cssSheet)));
-    }
+    if (candidate.canBeActivated(nullAtom))
+      collection.appendActiveStyleSheet(toCSSStyleSheet(sheet));
   }
 }
 
-void ShadowTreeStyleSheetCollection::updateActiveStyleSheets() {
+void ShadowTreeStyleSheetCollection::updateActiveStyleSheets(
+    StyleEngine& engine,
+    StyleResolverUpdateMode updateMode) {
   // StyleSheetCollection is GarbageCollected<>, allocate it on the heap.
   StyleSheetCollection* collection = StyleSheetCollection::create();
-  collectStyleSheets(*collection);
-  applyActiveStyleSheetChanges(*collection);
+  collectStyleSheets(engine, *collection);
+
+  StyleSheetChange change;
+  analyzeStyleSheetChange(updateMode, collection->activeAuthorStyleSheets(),
+                          change);
+
+  if (StyleResolver* styleResolver = engine.resolver()) {
+    if (change.styleResolverUpdateType != Additive) {
+      // We should not destroy StyleResolver when we find any stylesheet update
+      // in a shadow tree.  In this case, we will reset rulesets created from
+      // style elements in the shadow tree.
+      engine.resetAuthorStyle(treeScope());
+      styleResolver->removePendingAuthorStyleSheets(m_activeAuthorStyleSheets);
+      styleResolver->lazyAppendAuthorStyleSheets(
+          0, collection->activeAuthorStyleSheets());
+    } else {
+      styleResolver->lazyAppendAuthorStyleSheets(
+          m_activeAuthorStyleSheets.size(),
+          collection->activeAuthorStyleSheets());
+    }
+  }
+  if (change.requiresFullStyleRecalc)
+    toShadowRoot(treeScope().rootNode())
+        .host()
+        .setNeedsStyleRecalc(SubtreeStyleChange,
+                             StyleChangeReasonForTracing::create(
+                                 StyleChangeReason::ActiveStylesheetsUpdate));
+
+  collection->swap(*this);
+  collection->dispose();
 }
 
 }  // namespace blink