Use a new Supplement constructor for Supplement<Document> (Part 1)

third_party/WebKit/Source/core/css/CSSTiming.cpp

Index: third_party/WebKit/Source/core/css/CSSTiming.cpp
diff --git a/third_party/WebKit/Source/core/css/CSSTiming.cpp b/third_party/WebKit/Source/core/css/CSSTiming.cpp
index e38a4422796987bf221b0b4592327c7ffed0b6d6..abc70248ab611ce47641120fe93688cc6f4e4b30 100644
--- a/third_party/WebKit/Source/core/css/CSSTiming.cpp
+++ b/third_party/WebKit/Source/core/css/CSSTiming.cpp
@@ -31,12 +31,12 @@ void CSSTiming::recordUpdateDuration(double seconds) {
 }
 
 DEFINE_TRACE(CSSTiming) {
-  visitor->trace(m_document);
   visitor->trace(m_paintTiming);
   Supplement<Document>::trace(visitor);
 }
 
 CSSTiming::CSSTiming(Document& document)
-    : m_document(document), m_paintTiming(PaintTiming::from(document)) {}
+    : Supplement<Document>(document),
+      m_paintTiming(PaintTiming::from(document)) {}
 
 }  // namespace blink