Add separate blink_style category to blink style tracing

Source/core/dom/Document.cpp

Index: Source/core/dom/Document.cpp
diff --git a/Source/core/dom/Document.cpp b/Source/core/dom/Document.cpp
index bb638c79e5ba62286b6ea9d474350d927ae45288..cd1f453988f191fa7115e873f4c6e5fb25845c9b 100644
--- a/Source/core/dom/Document.cpp
+++ b/Source/core/dom/Document.cpp
@@ -1784,7 +1784,7 @@ void Document::updateRenderTree(StyleRecalcChange change)
 
 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;