Bug 1293613: An invalid or revoked MediaSource URI can't be trace to a MediaSource object. r=gerald

https://w3c.github.io/media-source/index.html#mediasource-attach: "If the resource fetch algorithm absolute URL matches the MediaSource object URL, ignore any preload attribute of the media element, skip any optional steps for when preload equals none"
A dummy URL or a revoked one no longer matches the MediaSource object URL, as such, the preload attribute isn't to be ignored.

MozReview-Commit-ID: EW5TOv9SSf

--HG--
extra : rebase_source : f3019139d5c6d198555dc623cd13d7294055e0f6

testing/web-platform/tests/media-source/mediasource-preload.html

@@ -64,11 +64,9 @@
 
             errorWithPreloadTest("auto", "revoked");
             errorWithPreloadTest("metadata", "revoked");
-            errorWithPreloadTest("none", "revoked");
 
             errorWithPreloadTest("auto", "corrupted");
             errorWithPreloadTest("metadata", "corrupted");
-            errorWithPreloadTest("none", "corrupted");
         </script>
     </body>
 </html>