Remove some unused code

Source/core/dom/StyleSheetCollection.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)
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
@@ skipping 32 matching lines @@
     m_activeAuthorStyleSheets.swap(other.m_activeAuthorStyleSheets);
 }
 
 void StyleSheetCollection::swapSheetsForSheetList(WillBeHeapVector<RefPtrWillBeMember<StyleSheet>>& sheets)
 {
     // Only called for collection of HTML Imports that never has active sheets.
     ASSERT(m_activeAuthorStyleSheets.isEmpty());
     m_styleSheetsForStyleSheetList.swap(sheets);
 }
 
-void StyleSheetCollection::appendActiveStyleSheets(const WillBeHeapVector<RefPtrWillBeMember<CSSStyleSheet>>& sheets)
-{
-    m_activeAuthorStyleSheets.appendVector(sheets);
-}
-
 void StyleSheetCollection::appendActiveStyleSheet(CSSStyleSheet* sheet)
 {
     m_activeAuthorStyleSheets.append(sheet);
 }
 
 void StyleSheetCollection::appendSheetForList(StyleSheet* sheet)
 {
     m_styleSheetsForStyleSheetList.append(sheet);
 }
 
 DEFINE_TRACE(StyleSheetCollection)
 {
     visitor->trace(m_activeAuthorStyleSheets);
     visitor->trace(m_styleSheetsForStyleSheetList);
 }
 
 }