Bug 1404187 - group timeout messages for MediaTestManager. r=kaku

So different test timeouts from the same test case will fall under the same bug.

MozReview-Commit-ID: LDstAhOpkYK

--HG--
extra : rebase_source : 9f2b52f237f18f3fecdd076295da4d43e5b30219

dom/media/test/manifest.js

@@ -1690,7 +1690,8 @@ function MediaTestManager() {
 
     var onTimeout = () => {
       this.hasTimeout = true;
-      ok(false, `${token} timed out!`);
+      ok(false, "Test timed out!");
+      info(`${token} timed out!`);
       this.finished(token);
     };
     // Default timeout to 180s for each test.