Avoid synchronous stylesheet update on html import loaded.

third_party/WebKit/Source/core/html/imports/HTMLImportChild.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 60 matching lines @@
   CreateCustomElementMicrotaskStepIfNeeded();
 }
 
 void HTMLImportChild::DidFinish() {
   if (client_)
     client_->DidFinish();
 }
 
 void HTMLImportChild::DidFinishLoading() {
   StateWillChange();
-  if (GetDocument() && GetDocument()->StyleSheets().length() > 0)
+  if (GetDocument() && GetDocument()->GetStyleEngine().HasStyleSheets())
     UseCounter::Count(Root()->GetDocument(),
                       UseCounter::kHTMLImportsHasStyleSheets);
   V0CustomElement::DidFinishLoadingImport(*(Root()->GetDocument()));
 }
 
 void HTMLImportChild::DidFinishUpgradingCustomElements() {
   StateWillChange();
   custom_element_microtask_step_.Clear();
 }
 
@@ skipping 99 matching lines @@
 #endif
 
 DEFINE_TRACE(HTMLImportChild) {
   visitor->Trace(custom_element_microtask_step_);
   visitor->Trace(loader_);
   visitor->Trace(client_);
   HTMLImport::Trace(visitor);
 }
 
 }  // namespace blink