Add LayoutTest for PerformanceObserver inside Worker

third_party/WebKit/LayoutTests/fast/workers/resources/worker-with-perfobs.js

+try {

[tdresser, 2017/07/04 14:31:46]

Rename file to worker-with-performance-observer.js.

It's nice to have this name be consistent between the html and the js.

[npm, 2017/07/07 14:45:08]

Done.

+  var obs = new PerformanceObserver(function () { return true; });

[tdresser, 2017/07/04 14:31:46]

We can use fancy new JS here, so we might as well make this a bit more modern.

var -> const (or just don't bother assigning it)

"function() {return true;}" -> "() => true"

So overall, that would just be:
new PerformanceObserver(() => true);

[npm, 2017/07/07 14:45:08]

Done.

+  postMessage("SUCCESS");
+}
+catch (ex) {

[tdresser, 2017/07/04 14:31:46]

Put on same line as closing brace above.

[npm, 2017/07/07 14:45:09]

Done.

+  postMessage("FAILURE");
+}