Use StyleEngine::resetAuthorStyle instead of clearScopedStyleResolver.

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

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/css/ActiveStyleSheets.h"
 
 #include "core/css/CSSStyleSheet.h"
 #include "core/css/RuleSet.h"
 #include "core/css/resolver/ScopedStyleResolver.h"
 #include "core/dom/ContainerNode.h"
@@ skipping 138 matching lines @@
   if (fontsChanged && change == ActiveSheetsChanged)
     engine.clearFontCache();
 
   // - If all sheets were removed, we remove the ScopedStyleResolver.
   // - If new sheets were appended to existing ones, start appending after the
   //   common prefix.
   // - For other diffs, reset author style and re-add all sheets for the
   //   TreeScope.
   if (treeScope.scopedStyleResolver()) {
     if (newStyleSheets.isEmpty())
-      treeScope.clearScopedStyleResolver();
+      engine.resetAuthorStyle(treeScope);
     else if (change == ActiveSheetsAppended)
       appendStartIndex = oldStyleSheets.size();
     else
       treeScope.scopedStyleResolver()->resetAuthorStyle();
   }
 
   if (!newStyleSheets.isEmpty()) {
     treeScope.ensureScopedStyleResolver().appendActiveStyleSheets(
         appendStartIndex, newStyleSheets);
   }
@@ skipping 17 matching lines @@
         .setNeedsStyleRecalc(SubtreeStyleChange,
                              StyleChangeReasonForTracing::create(
                                  StyleChangeReason::ActiveStylesheetsUpdate));
     return;
   }
 
   engine.scheduleInvalidationsForRuleSets(treeScope, changedRuleSets);
 }
 
 }  // namespace blink