Add separate blink_style category to blink style tracing

Source/core/dom/Document.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 1766 matching lines @@
 
     ASSERT(!m_timeline->hasOutdatedAnimationPlayer());
 
     TRACE_EVENT_END1(TRACE_DISABLED_BY_DEFAULT("devtools.timeline"), "RecalculateStyles", "elementCount", m_styleRecalcElementCounter);
     TRACE_EVENT_END1("blink", "Document::updateRenderTree", "elementCount", m_styleRecalcElementCounter);
     InspectorInstrumentation::didRecalculateStyle(cookie, m_styleRecalcElementCounter);
 }
 
 void Document::updateStyle(StyleRecalcChange change)
 {
-    TRACE_EVENT_BEGIN0("blink", "Document::updateStyle");
+    TRACE_EVENT_BEGIN0("blink,blink_style", "Document::updateStyle");
     unsigned initialResolverAccessCount = styleEngine().resolverAccessCount();
 
     HTMLFrameOwnerElement::UpdateSuspendScope suspendWidgetHierarchyUpdates;
     m_lifecycle.advanceTo(DocumentLifecycle::InStyleRecalc);
 
     NthIndexCache nthIndexCache(*this);
 
     if (styleChangeType() >= SubtreeStyleChange)
         change = Force;
 
@@ skipping 3962 matching lines @@
 #ifndef NDEBUG
 using namespace blink;
 void showLiveDocumentInstances()
 {
     WeakDocumentSet& set = liveDocumentSet();
     fprintf(stderr, "There are %u documents currently alive:\n", set.size());
     for (Document* document : set)
         fprintf(stderr, "- Document %p URL: %s\n", document, document->url().string().utf8().data());
 }
 #endif