Add UMA metric to track usage of sending a mousedown to select elements.

third_party/WebKit/LayoutTests/imported/wpt/dom/nodes/Document-createElementNS.html

Index: third_party/WebKit/LayoutTests/imported/wpt/dom/nodes/Document-createElementNS.html
diff --git a/third_party/WebKit/LayoutTests/imported/wpt/dom/nodes/Document-createElementNS.html b/third_party/WebKit/LayoutTests/imported/wpt/dom/nodes/Document-createElementNS.html
index a13c407e8d3f09a922c5750c900cae84eb278cf3..75005a09e2edbb796746b572f54785710473ec53 100644
--- a/third_party/WebKit/LayoutTests/imported/wpt/dom/nodes/Document-createElementNS.html
+++ b/third_party/WebKit/LayoutTests/imported/wpt/dom/nodes/Document-createElementNS.html
@@ -18,7 +18,6 @@ test(function() {
     [null, null, null],
     [null, "", "INVALID_CHARACTER_ERR"],
     [undefined, null, null],
-    [undefined, undefined, null],
     [undefined, "", "INVALID_CHARACTER_ERR"],
     ["http://example.com/", null, null],
     ["http://example.com/", "", "INVALID_CHARACTER_ERR"],
@@ -56,7 +55,7 @@ test(function() {
         assert_equals(element.nodeName, qualified)
         assert_equals(element.namespaceURI, namespace === undefined ? null : namespace)
       }
-    }, "createElementNS test " + i + ": " + t.map(function(el) { return format_value(el) }))
+    }, "createElementNS test: " + t.map(format_value))
   })
 })