Add trace event for updateActiveStyleSheets.

third_party/WebKit/Source/core/dom/StyleEngine.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, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 289 matching lines @@
 }
 
 void StyleEngine::updateActiveStyleSheets(StyleResolverUpdateMode updateMode)
 {
     ASSERT(isMaster());
     ASSERT(!document().inStyleRecalc());
 
     if (!document().isActive())
         return;
 
+    TRACE_EVENT0("blink,blink_style", "StyleEngine::updateActiveStyleSheets");
+
     if (shouldUpdateDocumentStyleSheetCollection(updateMode))
         documentStyleSheetCollection()->updateActiveStyleSheets(*this, updateMode);
 
     if (shouldUpdateShadowTreeStyleSheetCollection(updateMode)) {
         UnorderedTreeScopeSet treeScopesRemoved;
 
         if (updateMode == FullStyleUpdate) {
             for (TreeScope* treeScope : m_activeTreeScopes)
                 updateActiveStyleSheetsInShadow(updateMode, treeScope, treeScopesRemoved);
         } else {
@@ skipping 470 matching lines @@
     visitor->trace(m_dirtyTreeScopes);
     visitor->trace(m_activeTreeScopes);
     visitor->trace(m_fontSelector);
     visitor->trace(m_textToSheetCache);
     visitor->trace(m_sheetToTextCache);
 #endif
     CSSFontSelectorClient::trace(visitor);
 }
 
 } // namespace blink