Added trace for scheduleInvalidationsForRuleSets.

third_party/WebKit/Source/core/dom/StyleEngine.cpp

Index: third_party/WebKit/Source/core/dom/StyleEngine.cpp
diff --git a/third_party/WebKit/Source/core/dom/StyleEngine.cpp b/third_party/WebKit/Source/core/dom/StyleEngine.cpp
index 57e5ed09d1b8f3abbdbbb351f6b2041c7cee00b9..b225c0941afb20b79e1157522a89e75d7fd1788c 100644
--- a/third_party/WebKit/Source/core/dom/StyleEngine.cpp
+++ b/third_party/WebKit/Source/core/dom/StyleEngine.cpp
@@ -849,6 +849,9 @@ void StyleEngine::scheduleInvalidationsForRuleSets(
     DCHECK(!ruleSet->features().needsFullRecalcForRuleSetInvalidation());
 #endif  // DCHECK_IS_ON()
 
+  TRACE_EVENT0("blink,blink_style",
+               "StyleEngine::scheduleInvalidationsForRuleSets");
+
   bool invalidateSlotted = false;
   if (treeScope.rootNode().isShadowRoot()) {
     Element& host = toShadowRoot(treeScope.rootNode()).host();