Add detailed use counters for document.registerElement use.

third_party/WebKit/Source/core/dom/custom/V0CustomElementRegistry.cpp

Index: third_party/WebKit/Source/core/dom/custom/V0CustomElementRegistry.cpp
diff --git a/third_party/WebKit/Source/core/dom/custom/V0CustomElementRegistry.cpp b/third_party/WebKit/Source/core/dom/custom/V0CustomElementRegistry.cpp
index a5d3a780ccb7138a25f559d9fe41c96bf752fe45..f215786409159cbbdf4c725be929a569d32b1cec 100644
--- a/third_party/WebKit/Source/core/dom/custom/V0CustomElementRegistry.cpp
+++ b/third_party/WebKit/Source/core/dom/custom/V0CustomElementRegistry.cpp
@@ -38,7 +38,7 @@
 #include "core/dom/custom/CustomElementRegistry.h"
 #include "core/dom/custom/V0CustomElementException.h"
 #include "core/dom/custom/V0CustomElementRegistrationContext.h"
-#include "core/frame/LocalDOMWindow.h"
+#include "core/frame/UseCounter.h"
 
 namespace blink {
 
@@ -109,6 +109,18 @@ V0CustomElementDefinition* V0CustomElementRegistry::registerElement(
     return 0;
   }
 
+  if (validNames & V0CustomElement::EmbedderNames) {
+    UseCounter::count(document,
+                      UseCounter::V0CustomElementsRegisterEmbedderElement);
+  } else if (tagName.namespaceURI() == SVGNames::svgNamespaceURI) {
+    UseCounter::count(document, UseCounter::V0CustomElementsRegisterSVGElement);
+  } else {
+    UseCounter::count(
+        document, descriptor.isTypeExtension()
+                      ? UseCounter::V0CustomElementsRegisterHTMLTypeExtension
+                      : UseCounter::V0CustomElementsRegisterHTMLCustomTag);
+  }
+
   return definition;
 }