Avoid synchronous stylesheet update on html import loaded.

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All
  * rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved.
  * (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
@@ skipping 17 matching lines @@
 
 #include "core/dom/TreeScopeStyleSheetCollection.h"
 
 #include "core/css/ActiveStyleSheets.h"
 #include "core/css/CSSStyleSheet.h"
 #include "core/css/StyleRuleImport.h"
 #include "core/css/StyleSheetContents.h"
 #include "core/css/resolver/StyleResolver.h"
 #include "core/dom/Element.h"
 #include "core/dom/StyleEngine.h"
+#include "core/dom/StyleSheetCandidate.h"
 #include "core/html/HTMLLinkElement.h"
 #include "core/html/HTMLStyleElement.h"
 
 namespace blink {
 
 TreeScopeStyleSheetCollection::TreeScopeStyleSheetCollection(
     TreeScope& tree_scope)
     : tree_scope_(tree_scope) {}
 
 void TreeScopeStyleSheetCollection::AddStyleSheetCandidateNode(Node& node) {
@@ skipping 14 matching lines @@
 }
 
 void TreeScopeStyleSheetCollection::ApplyActiveStyleSheetChanges(
     StyleSheetCollection& new_collection) {
   GetDocument().GetStyleEngine().ApplyRuleSetChanges(
       GetTreeScope(), ActiveAuthorStyleSheets(),
       new_collection.ActiveAuthorStyleSheets());
   new_collection.Swap(*this);
 }
 
+bool TreeScopeStyleSheetCollection::HasStyleSheets() const {
+  for (Node* node : style_sheet_candidate_nodes_) {
+    StyleSheetCandidate candidate(*node);
+    if (candidate.Sheet() || candidate.IsEnabledAndLoading())
+      return true;
+  }
+  return false;
+}
+
 DEFINE_TRACE(TreeScopeStyleSheetCollection) {
   visitor->Trace(tree_scope_);
   visitor->Trace(style_sheet_candidate_nodes_);
   StyleSheetCollection::Trace(visitor);
 }
 
 }  // namespace blink