Fix flakyness in broadcastchannel/blobs.html test.

third_party/WebKit/LayoutTests/broadcastchannel/blobs.html

Index: third_party/WebKit/LayoutTests/broadcastchannel/blobs.html
diff --git a/third_party/WebKit/LayoutTests/broadcastchannel/blobs.html b/third_party/WebKit/LayoutTests/broadcastchannel/blobs.html
index a75be5e0e897501ed0ba2d62b9c54373502dab98..19f63bbad7f37e37186869e961737cb765b4d68b 100644
--- a/third_party/WebKit/LayoutTests/broadcastchannel/blobs.html
+++ b/third_party/WebKit/LayoutTests/broadcastchannel/blobs.html
@@ -33,15 +33,7 @@ async_test(t => {
     let c2 = new BroadcastChannel('blobworker');
     let events = [];
 
-    c1.onmessage = e => events.push(e.data);
-    c2.onmessage = e => events.push(e.data);
-    c2.addEventListener('message', e => {
-        if (e.data.blob)
-          c1.postMessage('done');
-      });
-
-    let worker = new Worker('resources/worker.js');
-    worker.onmessage = t.step_func(e => {
+    let verifyEvents = function() {

[jsbell, 2016/11/22 17:13:22]

nit: could be const, but using let for consistency with above is fine.

[Marijn Kruisselbrink, 2016/11/22 17:51:28]

Ah yes, good point. Changed all the lets that could be consts to const.

         assert_equals(events.length, 5);
         assert_equals(events[0], 'from worker');
         assert_equals(events[1], 'from worker');
@@ -57,6 +49,27 @@ async_test(t => {
             t.done();
           });
         reader.readAsText(events[3].blob);
+    };
+
+    let receivedDone = false;
+    let receivedWorkerDone = false;
+
+    c1.onmessage = e => events.push(e.data);
+    c2.onmessage = e => events.push(e.data);
+    c2.addEventListener('message', e => {

[jsbell, 2016/11/22 17:13:22]

Wrap in t.step_func()

[Marijn Kruisselbrink, 2016/11/22 17:51:28]

Done

+        if (e.data.blob)
+          c1.postMessage('done');
+        if (e.data === 'done')
+          receivedDone = true;
+        if (receivedDone && receivedWorkerDone)
+          verifyEvents();
+      });
+
+    let worker = new Worker('resources/worker.js');

[jsbell, 2016/11/22 17:13:23]

could be const, but let is okay.

+    worker.onmessage = t.step_func(e => {
+        receivedWorkerDone = true;
+        if (receivedDone && receivedWorkerDone)
+          verifyEvents();
       });
     worker.postMessage({channel: 'blobworker'});
     worker.postMessage({blob: ['hello-world']});