diff -r 000000000000 -r 6474c204b198 browser/devtools/webconsole/test/browser_webconsole_reflow.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/devtools/webconsole/test/browser_webconsole_reflow.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,35 @@
+/* vim:set ts=2 sw=2 sts=2 et: */
+/* 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/. */
+
+function test()
+{
+  addTab("data:text/html;charset=utf-8,Web Console test for reflow activity");
+
+  browser.addEventListener("load", function onLoad() {
+    browser.removeEventListener("load", onLoad, true);
+    openConsole(gBrowser.selectedTab, function(hud) {
+
+      function onReflowListenersReady(aType, aPacket) {
+        browser.contentDocument.body.style.display = "none";
+        browser.contentDocument.body.clientTop;
+      }
+
+      Services.prefs.setBoolPref("devtools.webconsole.filter.csslog", true);
+      hud.ui._updateReflowActivityListener(onReflowListenersReady);
+      Services.prefs.clearUserPref("devtools.webconsole.filter.csslog");
+
+      waitForMessages({
+        webconsole: hud,
+        messages: [{
+          text: /reflow: /,
+          category: CATEGORY_CSS,
+          severity: SEVERITY_LOG,
+        }],
+      }).then(() => {
+        finishTest();
+      });
+    });
+  }, true);
+}