Bug 1529867 - Wait for worker source, r=jlast.

Differential Revision: https://phabricator.services.mozilla.com/D25612

--HG--
extra : rebase_source : 940a415ade4c80a9fa884375749e2f4c9cc2cbf0

devtools/client/debugger/new/test/mochitest/browser_dbg-windowless-workers.js

@@ -43,6 +43,8 @@ add_task(async function() {
   const worker2Thread = workers[1].actor;
 
   const mainThreadSource = findSource(dbg, "doc-windowless-workers.html");
+
+  await waitForSource(dbg, "simple-worker.js");
   const workerSource = findSource(dbg, "simple-worker.js");
 
   info("Test pausing in the main thread");

devtools/client/debugger/new/test/mochitest/helpers.js

@@ -192,10 +192,7 @@ async function waitForSources(dbg, ...sources) {
 function waitForSource(dbg, url) {
   return waitForState(
     dbg,
-    state => {
-      const sources = dbg.selectors.getSources(state);
-      return Object.values(sources).find(s => (s.url || "").includes(url));
-    },
+    state => findSource(dbg, url, { silent: true }),
     "source exists"
   );
 }