[Invalidation Tracking] Trace ScheduleStyleInvalidation

Source/core/css/RuleFeature.cpp

Index: Source/core/css/RuleFeature.cpp
diff --git a/Source/core/css/RuleFeature.cpp b/Source/core/css/RuleFeature.cpp
index 272b9b06ce26109250e0f41884055f8a8e5f32f2..6d5d91a14408129b0e1de73e95f74328bb1a3756 100644
--- a/Source/core/css/RuleFeature.cpp
+++ b/Source/core/css/RuleFeature.cpp
@@ -37,6 +37,7 @@
 #include "core/css/invalidation/DescendantInvalidationSet.h"
 #include "core/dom/Element.h"
 #include "core/dom/Node.h"
+#include "core/inspector/InspectorTraceEvents.h"
 #include "wtf/BitVector.h"
 
 namespace blink {
@@ -188,11 +189,18 @@ static bool requiresSubtreeInvalidation(const CSSSelector& selector)
     }
 }
 
+static const unsigned char* s_tracingEnabled = nullptr;
+
+#define TRACE_SCHEDULE_STYLE_INVALIDATION_IF_ENABLED(...) \
+    if (UNLIKELY(*s_tracingEnabled)) \
+        TRACE_SCHEDULE_STYLE_INVALIDATION(__VA_ARGS__);
+
 RuleFeature::RuleFeature(StyleRule* rule, unsigned selectorIndex, bool hasDocumentSecurityOrigin)
     : rule(rule)
     , selectorIndex(selectorIndex)
     , hasDocumentSecurityOrigin(hasDocumentSecurityOrigin)
 {
+    s_tracingEnabled = TRACE_EVENT_API_GET_CATEGORY_ENABLED(TRACE_DISABLED_BY_DEFAULT("devtools.timeline.invalidationTracking"));

[rune, 2014/10/20 07:24:03]

This looks like a strange place to initialize that variable. RuleFeatures are
typically not created after you loaded your document. If I want to do tracing
with invalidationTracking enabled, I would typically do that after I loaded the
document to check the style invalidation effect of some user interaction?

[kouhei (in TOK), 2014/10/20 09:06:20]

Thanks for your comment.

This is a bit confusing (i'll add a comment later), but this is only caching the
pointer to the flag, so the flag itself can be changed afterwards.
The location of the flag doesn't change since tracing backend is initialized, so
ideally this can be done only once per renderer process.

[rune, 2014/10/20 09:18:18]

Yes, I see that now. Still, I think it would be better if this was exported as a
fast api from the tracing code instead if possible.

 }
 
 void RuleFeature::trace(Visitor* visitor)
@@ -598,33 +606,42 @@ void RuleFeatureSet::scheduleStyleInvalidationForClassChange(const SpaceSplitStr
 
 void RuleFeatureSet::scheduleStyleInvalidationForAttributeChange(const QualifiedName& attributeName, Element& element)
 {
-
-    if (RefPtrWillBeRawPtr<DescendantInvalidationSet> invalidationSet = m_attributeInvalidationSets.get(attributeName.localName()))
+    if (RefPtrWillBeRawPtr<DescendantInvalidationSet> invalidationSet = m_attributeInvalidationSets.get(attributeName.localName())) {
+        TRACE_SCHEDULE_STYLE_INVALIDATION_IF_ENABLED(element, *invalidationSet, attributeChange, attributeName);
         m_styleInvalidator.scheduleInvalidation(invalidationSet, element);
+    }
 }
 
 void RuleFeatureSet::scheduleStyleInvalidationForIdChange(const AtomicString& oldId, const AtomicString& newId, Element& element)
 {
     if (!oldId.isEmpty()) {
-        if (RefPtrWillBeRawPtr<DescendantInvalidationSet> invalidationSet = m_idInvalidationSets.get(oldId))
+        if (RefPtrWillBeRawPtr<DescendantInvalidationSet> invalidationSet = m_idInvalidationSets.get(oldId)) {
+            TRACE_SCHEDULE_STYLE_INVALIDATION_IF_ENABLED(element, *invalidationSet, idChange, oldId);
             m_styleInvalidator.scheduleInvalidation(invalidationSet, element);
+        }
     }
     if (!newId.isEmpty()) {
-        if (RefPtrWillBeRawPtr<DescendantInvalidationSet> invalidationSet = m_idInvalidationSets.get(newId))
+        if (RefPtrWillBeRawPtr<DescendantInvalidationSet> invalidationSet = m_idInvalidationSets.get(newId)) {
+            TRACE_SCHEDULE_STYLE_INVALIDATION_IF_ENABLED(element, *invalidationSet, idChange, newId);
             m_styleInvalidator.scheduleInvalidation(invalidationSet, element);
+        }
     }
 }
 
 void RuleFeatureSet::scheduleStyleInvalidationForPseudoChange(CSSSelector::PseudoType pseudo, Element& element)
 {
-    if (RefPtrWillBeRawPtr<DescendantInvalidationSet> invalidationSet = m_pseudoInvalidationSets.get(pseudo))
+    if (RefPtrWillBeRawPtr<DescendantInvalidationSet> invalidationSet = m_pseudoInvalidationSets.get(pseudo)) {
+        TRACE_SCHEDULE_STYLE_INVALIDATION_IF_ENABLED(element, *invalidationSet, pseudoChange, pseudo);
         m_styleInvalidator.scheduleInvalidation(invalidationSet, element);
+    }
 }
 
 void RuleFeatureSet::addClassToInvalidationSet(const AtomicString& className, Element& element)
 {
-    if (RefPtrWillBeRawPtr<DescendantInvalidationSet> invalidationSet = m_classInvalidationSets.get(className))
+    if (RefPtrWillBeRawPtr<DescendantInvalidationSet> invalidationSet = m_classInvalidationSets.get(className)) {
+        TRACE_SCHEDULE_STYLE_INVALIDATION_IF_ENABLED(element, *invalidationSet, classChange, className);
         m_styleInvalidator.scheduleInvalidation(invalidationSet, element);
+    }
 }
 
 StyleInvalidator& RuleFeatureSet::styleInvalidator()