1 files changed, 26 insertions, 0 deletions
diff --git a/browser/base/content/test/newtab/content-reflows.js b/browser/base/content/test/newtab/content-reflows.js
new file mode 100644
index 000000000..f1a53782e
--- /dev/null
+++ b/browser/base/content/test/newtab/content-reflows.js
@@ -0,0 +1,26 @@
+/* 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 () {
+  "use strict";
+
+  const Ci = Components.interfaces;
+
+  docShell.addWeakReflowObserver({
+    reflow() {
+      // Gather information about the current code path.
+      let path = (new Error().stack).split("\n").slice(1).join("\n");
+      if (path) {
+        sendSyncMessage("newtab-reflow", path);
+      }
+    },
+
+    reflowInterruptible() {
+      // We're not interested in interruptible reflows.
+    },
+
+    QueryInterface: XPCOMUtils.generateQI([Ci.nsIReflowObserver,
+                                           Ci.nsISupportsWeakReference])
+  });
+})();