Setting the link title may change the preferred set.

third_party/WebKit/Source/core/html/HTMLLinkElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Rob Buis (rwlbuis@gmail.com)
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 107 matching lines @@
     } else if (name == scopeAttr) {
         m_scope = value;
         process();
     } else if (name == disabledAttr) {
         UseCounter::count(document(), UseCounter::HTMLLinkElementDisabled);
         if (LinkStyle* link = linkStyle())
             link->setDisabledState(!value.isNull());
     } else {
         if (name == titleAttr) {
             if (LinkStyle* link = linkStyle())
-                link->setSheetTitle(value);
+                link->setSheetTitle(value, StyleEngine::UpdateActiveSheets);
         }
 
         HTMLElement::parseAttribute(name, oldValue, value);
     }
 }
 
 bool HTMLLinkElement::shouldLoadLink()
 {
     return isInDocumentTree() || (isConnected() && m_relAttribute.isStyleSheet());
 }
@@ skipping 328 matching lines @@
 
     if (StyleSheetContents* restoredSheet = const_cast<CSSStyleSheetResource*>(cachedStyleSheet)->restoreParsedStyleSheet(parserContext)) {
         DCHECK(restoredSheet->isCacheableForResource());
         DCHECK(!restoredSheet->isLoading());
 
         if (m_sheet)
             clearSheet();
         m_sheet = CSSStyleSheet::create(restoredSheet, m_owner);
         m_sheet->setMediaQueries(MediaQuerySet::create(m_owner->media()));
         if (m_owner->isInDocumentTree())
-            m_sheet->setTitle(m_owner->title());
+            setSheetTitle(m_owner->title());
         setCrossOriginStylesheetStatus(m_sheet.get());
 
         m_loading = false;
         restoredSheet->checkLoaded();
 
         restoredCachedStyleSheetHistogram.count(true);
         restoredCachedStyleSheet2Histogram.count(StyleSheetInMemoryCache);
         return;
     }
     restoredCachedStyleSheetHistogram.count(false);
     StyleSheetCacheStatus cacheStatus = cachedStyleSheet->response().wasCached() ? StyleSheetInDiskCache : StyleSheetNewEntry;
     restoredCachedStyleSheet2Histogram.count(cacheStatus);
 
     StyleSheetContents* styleSheet = StyleSheetContents::create(href, parserContext);
 
     if (m_sheet)
         clearSheet();
 
     m_sheet = CSSStyleSheet::create(styleSheet, m_owner);
     m_sheet->setMediaQueries(MediaQuerySet::create(m_owner->media()));
     if (m_owner->isInDocumentTree())
-        m_sheet->setTitle(m_owner->title());
+        setSheetTitle(m_owner->title());
     setCrossOriginStylesheetStatus(m_sheet.get());
 
     styleSheet->parseAuthorStyleSheet(cachedStyleSheet, m_owner->document().getSecurityOrigin());
 
     m_loading = false;
     styleSheet->notifyLoadedSheet(cachedStyleSheet);
     styleSheet->checkLoaded();
 
     if (styleSheet->isCacheableForResource())
         const_cast<CSSStyleSheetResource*>(cachedStyleSheet)->saveParsedStyleSheet(styleSheet);
@@ skipping 145 matching lines @@
             clearFetchFollowingCORS();
         }
 
         if (!m_owner->shouldLoadLink())
             return;
 
         m_loading = true;
 
         String title = m_owner->title();
         if (!title.isEmpty() && !m_owner->isAlternate() && m_disabledState != EnabledViaScript && m_owner->isInDocumentTree())
-            document().styleEngine().setPreferredStylesheetSetNameIfNotSet(title);
+            document().styleEngine().setPreferredStylesheetSetNameIfNotSet(title, StyleEngine::DontUpdateActiveSheets);
 
         bool mediaQueryMatches = true;
         LocalFrame* frame = loadingFrame();
         if (!m_owner->media().isEmpty() && frame) {
             MediaQuerySet* media = MediaQuerySet::create(m_owner->media());
             MediaQueryEvaluator evaluator(frame);
             mediaQueryMatches = evaluator.eval(media);
         }
 
         // Don't hold up layout tree construction and script execution on stylesheets
@@ skipping 27 matching lines @@
             notifyLoadedSheetAndAllCriticalSubresources(Node::ErrorOccurredLoadingSubresource);
         }
     } else if (m_sheet) {
         // we no longer contain a stylesheet, e.g. perhaps rel or type was changed
         StyleSheet* removedSheet = m_sheet.get();
         clearSheet();
         document().styleEngine().setNeedsActiveStyleUpdate(removedSheet, FullStyleUpdate);
     }
 }
 
-void LinkStyle::setSheetTitle(const String& title)
+void LinkStyle::setSheetTitle(const String& title, StyleEngine::ActiveSheetsUpdate updateActiveSheets)
 {
-    if (m_sheet && m_owner->isInDocumentTree())
+    if (!m_owner->isInDocumentTree() || !m_owner->relAttribute().isStyleSheet())
+        return;
+
+    if (m_sheet)
         m_sheet->setTitle(title);
+
+    if (title.isEmpty() || !isUnset() || m_owner->isAlternate())
+        return;
+
+    KURL href = m_owner->getNonEmptyURLAttribute(hrefAttr);
+    if (href.isValid() && !href.isEmpty())
+        document().styleEngine().setPreferredStylesheetSetNameIfNotSet(title, updateActiveSheets);
 }
 
 void LinkStyle::ownerRemoved()
 {
     if (m_sheet)
         clearSheet();
 
     if (styleSheetIsLoading())
         removePendingSheet();
 }
 
 DEFINE_TRACE(LinkStyle)
 {
     visitor->trace(m_sheet);
     LinkResource::trace(visitor);
     ResourceOwner<StyleSheetResource>::trace(visitor);
 }
 
 } // namespace blink