Measure the usage of <ol>.start with |reversed| and no |start| attribute.

third_party/WebKit/Source/core/html/HTMLOListElement.cpp

Index: third_party/WebKit/Source/core/html/HTMLOListElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLOListElement.cpp b/third_party/WebKit/Source/core/html/HTMLOListElement.cpp
index 5dcd6c6a07a666f186888b70930559bf202ff2bc..cfc1e949853a60695ae221785315ec34a2d23aee 100644
--- a/third_party/WebKit/Source/core/html/HTMLOListElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLOListElement.cpp
@@ -96,6 +96,19 @@ void HTMLOListElement::ParseAttribute(
   }
 }
 
+int HTMLOListElement::start() const {
+  if (has_explicit_start_)
+    return start_;
+
+  if (is_reversed_) {
+    UseCounter::Count(GetDocument(),
+                      UseCounter::kHTMLOListElementReversedWithoutStart);
+    return ItemCount();
+  }
+
+  return 1;
+}
+
 void HTMLOListElement::setStart(int start) {
   SetIntegralAttribute(startAttr, start);
 }