1 files changed, 132 insertions, 0 deletions
diff --git a/browser/base/content/test/performance/browser_window_resize.js b/browser/base/content/test/performance/browser_window_resize.js
new file mode 100644
index 0000000000..0838ae9f8f
--- /dev/null
+++ b/browser/base/content/test/performance/browser_window_resize.js
@@ -0,0 +1,132 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/**
+ * WHOA THERE: We should never be adding new things to EXPECTED_REFLOWS.
+ * Instead of adding reflows to the list, you should be modifying your code to
+ * avoid the reflow.
+ *
+ * See https://firefox-source-docs.mozilla.org/performance/bestpractices.html
+ * for tips on how to do that.
+ */
+const EXPECTED_REFLOWS = [
+  /**
+   * Nothing here! Please don't add anything new!
+   */
+];
+
+const gToolbar = document.getElementById("PersonalToolbar");
+
+/**
+ * Sets the visibility state on the Bookmarks Toolbar, and
+ * waits for it to transition to fully visible.
+ *
+ * @param visible (bool)
+ *        Whether or not the bookmarks toolbar should be made visible.
+ * @returns Promise
+ */
+async function toggleBookmarksToolbar(visible) {
+  let transitionPromise = BrowserTestUtils.waitForEvent(
+    gToolbar,
+    "transitionend",
+    e => e.propertyName == "max-height"
+  );
+
+  setToolbarVisibility(gToolbar, visible);
+  await transitionPromise;
+}
+
+/**
+ * Resizes a browser window to a particular width and height, and
+ * waits for it to reach a "steady state" with respect to its overflowing
+ * toolbars.
+ * @param win (browser window)
+ *        The window to resize.
+ * @param width (int)
+ *        The width to resize the window to.
+ * @param height (int)
+ *        The height to resize the window to.
+ * @returns Promise
+ */
+async function resizeWindow(win, width, height) {
+  let toolbarEvent = BrowserTestUtils.waitForEvent(
+    win,
+    "BookmarksToolbarVisibilityUpdated"
+  );
+  let resizeEvent = BrowserTestUtils.waitForEvent(win, "resize");
+  win.windowUtils.ensureDirtyRootFrame();
+  win.resizeTo(width, height);
+  await resizeEvent;
+  await toolbarEvent;
+}
+
+/*
+ * This test ensures that there are no unexpected
+ * uninterruptible reflows when resizing windows.
+ */
+add_task(async function () {
+  const BOOKMARKS_COUNT = 150;
+  const STARTING_WIDTH = 600;
+  const STARTING_HEIGHT = 400;
+  const SMALL_WIDTH = 150;
+  const SMALL_HEIGHT = 150;
+
+  await PlacesUtils.bookmarks.eraseEverything();
+
+  // Add a bunch of bookmarks to display in the Bookmarks toolbar
+  await PlacesUtils.bookmarks.insertTree({
+    guid: PlacesUtils.bookmarks.toolbarGuid,
+    children: Array(BOOKMARKS_COUNT)
+      .fill("")
+      // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+      .map((_, i) => ({ url: `http://test.places.${i}/` })),
+  });
+
+  let wasCollapsed = gToolbar.collapsed;
+  Assert.ok(wasCollapsed, "The toolbar is collapsed by default");
+  if (wasCollapsed) {
+    let promiseReady = BrowserTestUtils.waitForEvent(
+      gToolbar,
+      "BookmarksToolbarVisibilityUpdated"
+    );
+    await toggleBookmarksToolbar(true);
+    await promiseReady;
+  }
+
+  registerCleanupFunction(async () => {
+    if (wasCollapsed) {
+      await toggleBookmarksToolbar(false);
+    }
+    await PlacesUtils.bookmarks.eraseEverything();
+    await PlacesUtils.history.clear();
+  });
+
+  let win = await prepareSettledWindow();
+
+  if (
+    win.screen.availWidth < STARTING_WIDTH ||
+    win.screen.availHeight < STARTING_HEIGHT
+  ) {
+    Assert.ok(
+      false,
+      "This test is running on too small a display - " +
+        `(${STARTING_WIDTH}x${STARTING_HEIGHT} min)`
+    );
+    return;
+  }
+
+  await resizeWindow(win, STARTING_WIDTH, STARTING_HEIGHT);
+
+  await withPerfObserver(
+    async function () {
+      await resizeWindow(win, SMALL_WIDTH, SMALL_HEIGHT);
+      await resizeWindow(win, STARTING_WIDTH, STARTING_HEIGHT);
+    },
+    { expectedReflows: EXPECTED_REFLOWS, frames: { filter: () => [] } },
+    win
+  );
+
+  await BrowserTestUtils.closeWindow(win);
+});