diff --git a/browser/base/content/test/performance/browser.ini b/browser/base/content/test/performance/browser.ini
index b2546281e033..23b24d02542e 100644
--- a/browser/base/content/test/performance/browser.ini
+++ b/browser/base/content/test/performance/browser.ini
@@ -5,6 +5,7 @@ support-files =
   head.js
 [browser_appmenu_reflows.js]
 skip-if = asan || debug # Bug 1382809, bug 1369959
+[browser_favicon_load.js]
 [browser_startup.js]
 [browser_startup_content.js]
 skip-if = !e10s
diff --git a/browser/base/content/test/performance/browser_favicon_load.js b/browser/base/content/test/performance/browser_favicon_load.js
new file mode 100644
index 000000000000..4a979f57cf84
--- /dev/null
+++ b/browser/base/content/test/performance/browser_favicon_load.js
@@ -0,0 +1,176 @@
+/**
+ * Bug 1247843 - A test case for testing whether the channel used to load favicon
+ * has correct classFlags.
+ * Note that this test is modified based on browser_favicon_userContextId.js.
+ */
+
+const { classes: Cc, Constructor: CC, interfaces: Ci, utils: Cu } = Components;
+
+const TEST_SITE = "http://example.net";
+const TEST_THIRD_PARTY_SITE = "http://mochi.test:8888";
+
+const TEST_PAGE = TEST_SITE + "/browser/browser/components/originattributes/" +
+                  "test/browser/file_favicon.html";
+const FAVICON_URI = TEST_SITE + "/browser/browser/components/originattributes/" +
+                    "test/browser/file_favicon.png";
+const TEST_THIRD_PARTY_PAGE = "http://example.com/browser/browser/components/" +
+                              "originattributes/test/browser/file_favicon_thirdParty.html";
+const THIRD_PARTY_FAVICON_URI = TEST_THIRD_PARTY_SITE + "/browser/browser/components/" +
+                                "originattributes/test/browser/file_favicon.png";
+
+XPCOMUtils.defineLazyModuleGetter(this, "PromiseUtils",
+                                  "resource://gre/modules/PromiseUtils.jsm");
+
+let systemPrincipal = Services.scriptSecurityManager.getSystemPrincipal();
+
+function clearAllImageCaches() {
+  var tools = Cc["@mozilla.org/image/tools;1"]
+                .getService(SpecialPowers.Ci.imgITools);
+  var imageCache = tools.getImgCacheForDocument(window.document);
+  imageCache.clearCache(true);  // true=chrome
+  imageCache.clearCache(false); // false=content
+}
+
+function clearAllPlacesFavicons() {
+  return new Promise(resolve => {
+    Services.obs.addObserver(function observer() {
+      Services.obs.removeObserver(observer, "places-favicons-expired");
+      resolve();
+    }, "places-favicons-expired");
+
+    PlacesUtils.favicons.expireAllFavicons();
+  });
+}
+
+function FaviconObserver(aPageURI, aFaviconURL, aTailingEnabled) {
+  this.reset(aPageURI, aFaviconURL, aTailingEnabled);
+}
+
+FaviconObserver.prototype = {
+  observe(aSubject, aTopic, aData) {
+    // Make sure that the topic is 'http-on-modify-request'.
+    if (aTopic === "http-on-modify-request") {
+      let httpChannel = aSubject.QueryInterface(Ci.nsIHttpChannel);
+      let reqLoadInfo = httpChannel.loadInfo;
+      // Make sure this is a favicon request.
+      if (httpChannel.URI.spec !== this._faviconURL) {
+        return;
+      }
+
+      let cos = aSubject.QueryInterface(Ci.nsIClassOfService);
+      if (!cos) {
+        ok(false, "Http channel should implement nsIClassOfService.");
+        return;
+      }
+
+      if (!reqLoadInfo) {
+        ok(false, "Should have load info.");
+        return;
+      }
+
+      let loadingPrincipal = reqLoadInfo.loadingPrincipal;
+
+      if (loadingPrincipal.equals(systemPrincipal)) {
+        this._faviconReqXUL = true;
+      } else {
+        this._faviconReqPlaces = true;
+      }
+
+      let haveTailFlag = !!(cos.classFlags & Ci.nsIClassOfService.Tail);
+      info("classFlags=" + cos.classFlags);
+      is(haveTailFlag, this._tailingEnabled, "Should have correct cos flag.");
+    } else {
+      ok(false, "Received unexpected topic: ", aTopic);
+    }
+
+    if (this._faviconReqXUL && this._faviconReqPlaces) {
+      this._faviconLoaded.resolve();
+    }
+  },
+
+  reset(aPageURI, aFaviconURL, aTailingEnabled) {
+    this._faviconReqXUL = false;
+    this._faviconReqPlaces = false;
+    this._faviconURL = aFaviconURL;
+    this._faviconLoaded = PromiseUtils.defer();
+    this._tailingEnabled = aTailingEnabled;
+  },
+
+  get promise() {
+    return this._faviconLoaded.promise;
+  }
+};
+
+function waitOnFaviconLoaded(aFaviconURL) {
+  return PlacesTestUtils.waitForNotification(
+    "onPageChanged",
+    (uri, attr, value, id) => attr === Ci.nsINavHistoryObserver.ATTRIBUTE_FAVICON &&
+                              value === aFaviconURL,
+    "history");
+}
+
+async function doTest(aTestPage, aFaviconURL, aTailingEnabled) {
+  let pageURI = Services.io.newURI(aTestPage);
+
+  // Create the observer object for observing favion channels.
+  let observer = new FaviconObserver(pageURI, aFaviconURL, aTailingEnabled);
+
+  let promiseWaitOnFaviconLoaded = waitOnFaviconLoaded(aFaviconURL);
+
+  // Add the observer earlier in case we miss it.
+  Services.obs.addObserver(observer, "http-on-modify-request");
+
+  // Open the tab.
+  let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, aTestPage);
+  // Waiting for favicon requests are all made.
+  await observer.promise;
+  // Waiting for favicon loaded.
+  await promiseWaitOnFaviconLoaded;
+
+  // Close the tab.
+  await BrowserTestUtils.removeTab(tab);
+}
+
+async function setupTailingPreference(aTailingEnabled) {
+  await SpecialPowers.pushPrefEnv({"set": [
+      ["network.http.tailing.enabled", aTailingEnabled]
+  ]});
+}
+
+async function cleanup() {
+  // Clear all cookies.
+  Services.cookies.removeAll();
+  // Clear cache.
+  Services.cache2.clear();
+  // Clear Places favicon caches.
+  await clearAllPlacesFavicons();
+  // Clear all image caches and network caches.
+  clearAllImageCaches();
+  // Clear Places history.
+  await PlacesUtils.history.clear();
+}
+
+// A clean up function to prevent affecting other tests.
+registerCleanupFunction(async () => {
+  await cleanup();
+});
+
+add_task(async function test_favicon_with_tailing_enabled() {
+  await cleanup();
+
+  let tailingEnabled = true;
+
+  await setupTailingPreference(tailingEnabled);
+
+  await doTest(TEST_PAGE, FAVICON_URI, tailingEnabled);
+});
+
+add_task(async function test_favicon_with_tailing_disabled() {
+  await cleanup();
+
+  let tailingEnabled = false;
+
+  await setupTailingPreference(tailingEnabled);
+
+  await doTest(TEST_THIRD_PARTY_PAGE, THIRD_PARTY_FAVICON_URI, tailingEnabled);
+});