Bug 1708446 - Add a browser mochitest to make sure the jank notification works properly for popup windows in the browser process. r=boris,botond,sotaro

Differential Revision: https://phabricator.services.mozilla.com/D116186

gfx/tests/browser/browser.ini

@@ -5,4 +5,8 @@ support-files =
 support-files =
   file_native_font_cache_macos.html
 skip-if = (os != 'mac')
+[browser_partial_prerender_animation_in_popup.js]
+support-files =
+  !/dom/animation/test/testcommon.js
+skip-if = (os == 'mac') # on Mac popup windows use basic layers so animation can't be run on the compositor
 [browser_windowless_troubleshoot_crash.js]

gfx/tests/browser/browser_partial_prerender_animation_in_popup.js

@@ -0,0 +1,90 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/* import-globals-from ../../../dom/animation/test/testcommon.js */
+Services.scriptloader.loadSubScript(
+  "chrome://mochitests/content/tests/dom/animation/test/testcommon.js",
+  this
+);
+
+add_task(async () => {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["layout.animation.prerender.partial", true],
+      ["layout.animation.prerender.viewport-ratio-limit", 1.125],
+    ],
+  });
+
+  let navBar = document.getElementById("nav-bar");
+
+  const anchor = document.createXULElement("toolbarbutton");
+  anchor.classList.add("toolbarbutton-1", "chromeclass-toolbar-additional");
+  navBar.appendChild(anchor);
+
+  // Prepare a popup panel.
+  const panel = document.createXULElement("panel");
+  panel.setAttribute("noautohide", true);
+  navBar.appendChild(panel);
+
+  // Add a overflow:scroll container to avoid expanding the popup window size.
+  const container = document.createElement("div");
+  container.style = "width: 100px; height: 100px; overflow: scroll;";
+
+  // Looks like in popup window wider elements in the overflow:scroll container
+  // are still affecting the viewport size of the popup content, for example,
+  // if we specify "witdh: 800px" here, this element is not going to be partial-
+  // prerendered, it will be fully prerendered, so we use vertically overflowed
+  // element here.
+  const target = document.createElement("div");
+  target.style = "width: 100px; height: 800px;";
+
+  container.appendChild(target);
+  panel.appendChild(container);
+
+  registerCleanupFunction(() => {
+    panel.remove();
+    anchor.remove();
+  });
+
+  panel.openPopup(anchor);
+
+  // Start a transform transition with a 1s delay step-start function so that
+  // we can ensure that
+  // 1) when the target element is initially composited on the compositor the
+  //    transition hasn't yet started, thus no jank happens
+  // 2) when the transition starts on the compositor thread, it causes a jank
+  //    so that it will report back to the main-thread
+  target.style.transition = "transform 100s step-start 1s";
+  getComputedStyle(target);
+  const startTransition = new Promise(resolve => {
+    target.addEventListener("transitionstart", resolve);
+  });
+  target.style.transform = "translateY(-130px)";
+  const transition = target.getAnimations()[0];
+
+  // Wait for the transition start.
+  await startTransition;
+
+  // Make sure it's running on the compositor.
+  Assert.ok(
+    transition.isRunningOnCompositor,
+    "The transition should be running on the compositor thread"
+  );
+
+  // Collect restyling markers in 5 frames.
+  const markers = await observeStylingInTargetWindow(panel.ownerGlobal, 5);
+
+  // On non WebRender we observe two restyling markers because we get the second
+  // jank report from the compositor thread before a new pre-rendered result,
+  // which was triggered by the first jank report, reached to the compositor
+  // thread. So we allow one or two makers here.
+  // NOTE: Since we wrap the target element in overflow:scroll container, we
+  // might see an additional restyling marker triggered by
+  // KeyframeEffect::OverflowRegionRefreshInterval (200ms) on very slow
+  // platforms (e.g. TSAN builds), if it happens we should allow the additional
+  // restyling here.
+  Assert.greaterOrEqual(markers.length, 1);
+  Assert.lessOrEqual(markers.length, 2);
+});