Avoid stack allocating StyleSheetCollections.

third_party/WebKit/Source/core/dom/DocumentStyleSheetCollection.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 70 matching lines @@
 
 void DocumentStyleSheetCollection::collectStyleSheets(StyleEngine& engine, DocumentStyleSheetCollector& collector)
 {
     DCHECK_EQ(&document().styleEngine(), &engine);
     collector.appendActiveStyleSheets(engine.injectedAuthorStyleSheets());
     collectStyleSheetsFromCandidates(engine, collector);
 }
 
 void DocumentStyleSheetCollection::updateActiveStyleSheets(StyleEngine& engine, StyleResolverUpdateMode updateMode)
 {
-    StyleSheetCollection collection;
-    ActiveDocumentStyleSheetCollector collector(collection);
+    // StyleSheetCollection is GarbageCollected<>, allocate it on the heap.
+    StyleSheetCollection* collection = StyleSheetCollection::create();
+    ActiveDocumentStyleSheetCollector collector(*collection);
     collectStyleSheets(engine, collector);
 
     StyleSheetChange change;
-    analyzeStyleSheetChange(updateMode, collection, change);
+    analyzeStyleSheetChange(updateMode, collection->activeAuthorStyleSheets(), change);
 
     if (change.styleResolverUpdateType == Reconstruct) {
         engine.clearMasterResolver();
         // TODO(rune@opera.com): The following depends on whether StyleRuleFontFace was modified or not.
         // We should only remove modified/removed @font-face rules, or @font-face rules from removed
         // stylesheets. We currently avoid clearing the font cache when we have had an analyzed update
         // and no @font-face rules were removed, in which case requiresFullStyleRecalc will be false.
         if (change.requiresFullStyleRecalc)
             engine.clearFontCache();
     } else if (StyleResolver* styleResolver = engine.resolver()) {
         if (change.styleResolverUpdateType != Additive) {
             DCHECK_EQ(change.styleResolverUpdateType, Reset);
             styleResolver->resetAuthorStyle(treeScope());
             engine.removeFontFaceRules(change.fontFaceRulesToRemove);
             styleResolver->removePendingAuthorStyleSheets(m_activeAuthorStyleSheets);
-            styleResolver->lazyAppendAuthorStyleSheets(0, collection.activeAuthorStyleSheets());
+            styleResolver->lazyAppendAuthorStyleSheets(0, collection->activeAuthorStyleSheets());
         } else {
-            styleResolver->lazyAppendAuthorStyleSheets(m_activeAuthorStyleSheets.size(), collection.activeAuthorStyleSheets());
+            styleResolver->lazyAppendAuthorStyleSheets(m_activeAuthorStyleSheets.size(), collection->activeAuthorStyleSheets());
         }
     }
     if (change.requiresFullStyleRecalc)
         document().setNeedsStyleRecalc(SubtreeStyleChange, StyleChangeReasonForTracing::create(StyleChangeReason::ActiveStylesheetsUpdate));
 
-    collection.swap(*this);
+    collection->swap(*this);
+    collection->dispose();
 }
 
 DEFINE_TRACE_WRAPPERS(DocumentStyleSheetCollection)
 {
     for (auto sheet : m_styleSheetsForStyleSheetList) {
         visitor->traceWrappers(sheet);
     }
 }
 } // namespace blink