Enable vulcanizing perf_insights mapper

tracing/tracing/base/base.html

Index: tracing/tracing/base/base.html
diff --git a/tracing/tracing/base/base.html b/tracing/tracing/base/base.html
index 9c9254b6c7f3ac8e79ce9745cef4437dc32602b5..983d86f5d5b6c15b20892e0368ac86f499350dd0 100644
--- a/tracing/tracing/base/base.html
+++ b/tracing/tracing/base/base.html
@@ -175,6 +175,14 @@ this.tr = (function() {
       tr.isLinux = /Linux/.test(navigator.userAgent);
     }
     tr.isHeadless = tr.isVinn || tr.isNode;
+
+    // Workaround for Library requiring window.
+    if (tr.isHeadless) {
+      /**
+       * Hack.
+       */
+      global.window = {};
+    }
   }
 
   return {