Bug 1363505 - Add tab switch reflow test. r=florian on a CLOSED TREE
authorMike Conley <mconley@mozilla.com>
Thu, 25 May 2017 16:05:53 -0400
changeset 400884 8bd3380db77f9c6cc5e3ee8f7adc84b939d6076a
parent 400883 1ae492c2da06f838a2ebe6a639068fbe6b080d8c
child 400885 920a7465a372947b9b7ac096c6ae82a2449276e8
child 400931 b138d2f271fdb598bf8a66c2dcb7fe391ca2a96f
push id57
push userfmarier@mozilla.com
push dateSat, 24 Jun 2017 00:05:50 +0000
reviewersflorian
bugs1363505
milestone55.0a1
Bug 1363505 - Add tab switch reflow test. r=florian on a CLOSED TREE MozReview-Commit-ID: 9A77Fi6Kroi
browser/base/content/test/performance/browser.ini
browser/base/content/test/performance/browser_tabswitch_reflows.js
--- a/browser/base/content/test/performance/browser.ini
+++ b/browser/base/content/test/performance/browser.ini
@@ -1,11 +1,12 @@
 [DEFAULT]
 support-files =
   head.js
 [browser_startup.js]
 [browser_tabclose_grow_reflows.js]
 [browser_tabclose_reflows.js]
 [browser_tabopen_reflows.js]
 [browser_tabopen_squeeze_reflows.js]
+[browser_tabswitch_reflows.js]
 [browser_toolbariconcolor_restyles.js]
 [browser_windowclose_reflows.js]
 [browser_windowopen_reflows.js]
new file mode 100644
--- /dev/null
+++ b/browser/base/content/test/performance/browser_tabswitch_reflows.js
@@ -0,0 +1,53 @@
+/* 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. This
+ * is a whitelist that should slowly go away as we improve the performance of
+ * the front-end. Instead of adding more reflows to the whitelist, you should
+ * be modifying your code to avoid the reflow.
+ *
+ * See https://developer.mozilla.org/en-US/Firefox/Performance_best_practices_for_Firefox_fe_engineers
+ * for tips on how to do that.
+ */
+const EXPECTED_REFLOWS = [
+  /**
+   * Nothing here! Please don't add anything new!
+   */
+];
+
+/*
+ * This test ensures that there are no unexpected
+ * uninterruptible reflows when switching between two
+ * tabs that are both fully visible.
+ */
+add_task(async function() {
+  await ensureNoPreloadedBrowser();
+
+  // At the time of writing, there are no reflows on simple tab switching.
+  // Mochitest will fail if we have no assertions, so we add one here
+  // to make sure nobody adds any new ones.
+  Assert.equal(EXPECTED_REFLOWS.length, 0,
+    "We shouldn't have added any new expected reflows.");
+
+  // Because the tab strip is a scrollable frame, we can't use the
+  // default dirtying function from withReflowObserver and reliably
+  // get reflows for the strip. Instead, we provide a node that's
+  // already in the scrollable frame to dirty - in this case, the
+  // original tab.
+  let origTab = gBrowser.selectedTab;
+
+  let firstSwitchDone = BrowserTestUtils.waitForEvent(window, "TabSwitchDone");
+  let otherTab = await BrowserTestUtils.openNewForegroundTab(gBrowser);
+  await firstSwitchDone;
+
+  await withReflowObserver(async function() {
+    let switchDone = BrowserTestUtils.waitForEvent(window, "TabSwitchDone");
+    gBrowser.selectedTab = origTab;
+    await switchDone;
+  }, EXPECTED_REFLOWS, window, origTab);
+
+  await BrowserTestUtils.removeTab(otherTab);
+});