1 files changed, 74 insertions, 0 deletions
diff --git a/toolkit/content/tests/browser/browser_starting_autoscroll_in_about_content.js b/toolkit/content/tests/browser/browser_starting_autoscroll_in_about_content.js
new file mode 100644
index 0000000000..f0daa480d4
--- /dev/null
+++ b/toolkit/content/tests/browser/browser_starting_autoscroll_in_about_content.js
@@ -0,0 +1,74 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_task(async function testStartingAutoScrollInAboutContent() {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["general.autoScroll", true],
+      ["middlemouse.contentLoadURL", false],
+      ["test.events.async.enabled", true],
+    ],
+  });
+
+  await BrowserTestUtils.withNewTab("about:support", async function (browser) {
+    let autoScroller;
+    let promiseStartAutoScroll = new Promise(resolve => {
+      let onPopupShown = event => {
+        if (event.originalTarget.id != "autoscroller") {
+          return;
+        }
+        autoScroller = event.originalTarget;
+        info('"popupshown" event is fired');
+        autoScroller.getBoundingClientRect(); // Flush layout of the autoscroller
+        resolve();
+      };
+      window.addEventListener("popupshown", onPopupShown, { capture: true });
+      registerCleanupFunction(() => {
+        window.removeEventListener("popupshown", onPopupShown, {
+          capture: true,
+        });
+      });
+    });
+
+    ok(!browser.isRemoteBrowser, "Browser should not be remote.");
+    await ContentTask.spawn(browser, null, async function () {
+      await ContentTaskUtils.waitForCondition(
+        () =>
+          content.document.documentElement.scrollHeight >
+          content.document.documentElement.clientHeight,
+        "The document should become scrollable"
+      );
+    });
+
+    await EventUtils.promiseNativeMouseEvent({
+      type: "mousemove",
+      target: browser,
+      offsetX: 10,
+      offsetY: 10, // XXX Assuming that there is no interactive content here.
+    });
+    await EventUtils.promiseNativeMouseEvent({
+      type: "mousedown",
+      button: 1, // middle click
+      target: browser,
+      offsetX: 10,
+      offsetY: 10,
+    });
+    info("Waiting to start autoscrolling");
+    await promiseStartAutoScroll;
+    ok(autoScroller != null, "Autoscrolling should be started");
+    await EventUtils.promiseNativeMouseEvent({
+      type: "mouseup",
+      button: 1, // middle click
+      target: browser,
+      offsetX: 10,
+      offsetY: 10,
+    }); // release implicit capture
+    EventUtils.synthesizeKey("KEY_Escape"); // Close autoscroller
+    await TestUtils.waitForCondition(
+      () => autoScroller.state == "closed",
+      "autoscroll should be canceled"
+    );
+  });
+});