Fill in descriptions on relevant blink_perf tests

PerformanceTests/DOM/textarea-dom.html

Index: PerformanceTests/DOM/textarea-dom.html
diff --git a/PerformanceTests/DOM/textarea-dom.html b/PerformanceTests/DOM/textarea-dom.html
index d52ec19a031f7f0383582379ee584b43175db812..b9bd1e2a181007f43bc51cd51e649299985815bb 100644
--- a/PerformanceTests/DOM/textarea-dom.html
+++ b/PerformanceTests/DOM/textarea-dom.html
@@ -16,10 +16,14 @@ var nodes = [];
 var childCount = 1000;
 for (var i = 0; i < childCount; ++i)
     nodes.push(document.createTextNode('A quick brown fox jumps over the lazy dog.\n'));
-PerfTestRunner.measureRunsPerSecond({run: function() {
-    for (var i = 0; i < childCount; ++i)
-        container.appendChild(nodes[i]);
-    container.innerHTML = '';
-}});
+
+PerfTestRunner.measureRunsPerSecond({
+    description: "Measures performance of adding text nodes to a textarea, then clearing it.",
+    run: function() {
+        for (var i = 0; i < childCount; ++i)
+            container.appendChild(nodes[i]);
+        container.innerHTML = '';
+    }
+});
 </script>
 </body>