Backend for css rule tracking

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

Index: third_party/WebKit/Source/core/dom/StyleEngine.h
diff --git a/third_party/WebKit/Source/core/dom/StyleEngine.h b/third_party/WebKit/Source/core/dom/StyleEngine.h
index 3613b7247870ba5600efbc209b1f64f4f8c8bed4..d0912d9415324e37a90905c6f6832dfc61787c11 100644
--- a/third_party/WebKit/Source/core/dom/StyleEngine.h
+++ b/third_party/WebKit/Source/core/dom/StyleEngine.h
@@ -58,6 +58,7 @@ class Node;
 class RuleFeatureSet;
 class ShadowTreeStyleSheetCollection;
 class StyleRuleFontFace;
+class StyleRuleUsageTracker;
 class StyleSheet;
 class StyleSheetContents;
 class ViewportStyleResolver;
@@ -172,6 +173,8 @@ class CORE_EXPORT StyleEngine final
 
   StyleResolver* resolver() const { return m_resolver; }
 
+  void setRuleUsageTracker(StyleRuleUsageTracker*);
+
   StyleResolver& ensureResolver() {
     if (!m_resolver) {
       createResolver();
@@ -319,6 +322,8 @@ class CORE_EXPORT StyleEngine final
   TraceWrapperMember<DocumentStyleSheetCollection>
       m_documentStyleSheetCollection;
 
+  Member<StyleRuleUsageTracker> m_tracker;
+
   typedef HeapHashMap<WeakMember<TreeScope>,
                       Member<ShadowTreeStyleSheetCollection>>
       StyleSheetCollectionMap;