Bug 1443942 - Make redirect SJS' serve with headers to prevent Necko caching. r=jya

Try to prevent Necko from caching the results of our SJS media responses, as
some of the test that use it rely on the server being hit and serving a
redirect. Sometimes the tests which rely on hitting a redirect in an SJS
where timing out without this, as Necko would cache the response and not
hit the server, and so not hit the redirect.

Also include a noise parameter to increase the likelihood that the URL is
unique, to further reduce the chance that Necko caches the result.

MozReview-Commit-ID: 3cLEiDoh4HG

--HG--
extra : rebase_source : 24c152d46540866f14211fae30f1e59c5d23b6d4

dom/media/test/dynamic_redirect.sjs

@@ -63,6 +63,7 @@ function handleRequest(request, response)
   response.setHeader("Content-Length", contentLength, false);
   response.setHeader("Content-Type", type, false);
   response.setHeader("Accept-Ranges", "bytes", false);
+  response.setHeader("Cache-Control", "no-cache, no-store, must-revalidate");
   response.write(byterange, byterange.length);
   bis.close();
 }

dom/media/test/midflight-redirect.sjs

@@ -64,6 +64,7 @@ function handleRequest(request, response)
   response.setHeader("Content-Length", contentLength, false);
   response.setHeader("Content-Type", type, false);
   response.setHeader("Accept-Ranges", "bytes", false);
+  response.setHeader("Cache-Control", "no-cache, no-store, must-revalidate");
   if (redirected && useCors) {
     response.setHeader("Access-Control-Allow-Origin", "*");
   }

dom/media/test/test_midflight_redirect_blocked.html

@@ -41,9 +41,11 @@
             removeNodeAndSource(element);
           }, false);
 
+          var noise = Math.floor(Math.random() * 100000000);
           element.src = "midflight-redirect.sjs?resource=" + test.name
                       + (useCors ? "&cors" : "")
-                      + "&type=" + test.type;
+                      + "&type=" + test.type
+                      + "&noise=" + noise;
           element.preload = "metadata";
           document.body.appendChild(element);
           element.load()