diff -r 000000000000 -r 6474c204b198 toolkit/components/mediasniffer/test/unit/test_mediasniffer.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/components/mediasniffer/test/unit/test_mediasniffer.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,98 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const Ci = Components.interfaces;
+const Cu = Components.utils;
+
+Cu.import("resource://testing-common/httpd.js");
+
+const PATH = "/file.meh";
+var httpserver = new HttpServer();
+
+// Each time, the data consist in a string that should be sniffed as Ogg.
+const data = "OggS\0meeeh.";
+var testRan = 0;
+
+// If the content-type is not present, or if it's application/octet-stream, it
+// should be sniffed to application/ogg by the media sniffer. Otherwise, it
+// should not be changed.
+const tests = [
+  // Those three first case are the case of a media loaded in a media element.
+  // The first two should be sniffeed.
+  { contentType: "",
+    expectedContentType: "application/ogg",
+    flags: Ci.nsIChannel.LOAD_TREAT_APPLICATION_OCTET_STREAM_AS_UNKNOWN },
+  { contentType: "application/octet-stream",
+    expectedContentType: "application/ogg",
+    flags: Ci.nsIChannel.LOAD_TREAT_APPLICATION_OCTET_STREAM_AS_UNKNOWN },
+  { contentType: "application/something",
+    expectedContentType: "application/something",
+    flags: Ci.nsIChannel.LOAD_TREAT_APPLICATION_OCTET_STREAM_AS_UNKNOWN },
+  // This last case tests the case of a channel opened while allowing content
+  // sniffers to override the content-type, like in the docshell.
+  { contentType: "application/octet-stream",
+    expectedContentType: "application/ogg",
+    flags: Ci.nsIChannel.LOAD_CALL_CONTENT_SNIFFERS },
+  { contentType: "",
+    expectedContentType: "application/ogg",
+    flags: Ci.nsIChannel.LOAD_CALL_CONTENT_SNIFFERS },
+];
+
+// A basic listener that reads checks the if we sniffed properly.
+var listener = {
+  onStartRequest: function(request, context) {
+    do_check_eq(request.QueryInterface(Ci.nsIChannel).contentType,
+                tests[testRan].expectedContentType);
+  },
+
+  onDataAvailable: function(request, context, stream, offset, count) {
+    try {
+      var bis = Components.classes["@mozilla.org/binaryinputstream;1"]
+                          .createInstance(Components.interfaces.nsIBinaryInputStream);
+      bis.setInputStream(stream);
+      bis.readByteArray(bis.available());
+    } catch (ex) {
+      do_throw("Error in onDataAvailable: " + ex);
+    }
+  },
+
+  onStopRequest: function(request, context, status) {
+    testRan++;
+    runNext();
+  }
+};
+
+function setupChannel(url, flags)
+{
+  var ios = Components.classes["@mozilla.org/network/io-service;1"].
+                       getService(Ci.nsIIOService);
+  var chan = ios.newChannel("http://localhost:" +
+                           httpserver.identity.primaryPort + url, "", null);
+  chan.loadFlags |= flags;
+  var httpChan = chan.QueryInterface(Components.interfaces.nsIHttpChannel);
+  return httpChan;
+}
+
+function runNext() {
+  if (testRan == tests.length) {
+    do_test_finished();
+    return;
+  }
+  var channel = setupChannel(PATH, tests[testRan].flags);
+  httpserver.registerPathHandler(PATH, function(request, response) {
+    response.setHeader("Content-Type", tests[testRan].contentType, false);
+    response.bodyOutputStream.write(data, data.length);
+  });
+  channel.asyncOpen(listener, channel, null);
+}
+
+function run_test() {
+  httpserver.start(-1);
+  do_test_pending();
+  try {
+    runNext();
+  } catch (e) {
+    print("ERROR - " + e + "\n");
+  }
+}