Backport the long-sibling-list perf test to reference build DOM APIs.

third_party/WebKit/PerformanceTests/DOM/long-sibling-list.html

Index: third_party/WebKit/PerformanceTests/DOM/long-sibling-list.html
diff --git a/third_party/WebKit/PerformanceTests/DOM/long-sibling-list.html b/third_party/WebKit/PerformanceTests/DOM/long-sibling-list.html
index fb418b51ed5bc6f87a52ee07fe5ac6380521193d..5e7b870ae2271fcf20aa77d4040cbe7db0aa1689 100644
--- a/third_party/WebKit/PerformanceTests/DOM/long-sibling-list.html
+++ b/third_party/WebKit/PerformanceTests/DOM/long-sibling-list.html
@@ -12,12 +12,12 @@ PerfTestRunner.measureRunsPerSecond({
     PerfTestRunner.gc();
   },
   run: () => {
-    const num_words = 1000;
-    for (let i = 0; i < num_words; i++) {
-      let a = document.createElement('a');
-      a.append(i);
-      container.append(a);
-      container.append(' ');
+    const num_words = 300;
+    for (var i = 0; i < num_words; i++) {
+      var a = document.createElement('a');
+      a.appendChild(document.createTextNode('' + i));
+      container.appendChild(a);
+      container.appendChild(document.createTextNode(' '));
     }
     PerfTestRunner.forceLayout();
   }