1 files changed, 136 insertions, 0 deletions
diff --git a/browser/base/content/test/performance/browser_startup_images.js b/browser/base/content/test/performance/browser_startup_images.js
new file mode 100644
index 0000000000..5a27b9a8dd
--- /dev/null
+++ b/browser/base/content/test/performance/browser_startup_images.js
@@ -0,0 +1,136 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/**
+ * This test checks that any images we load on startup are actually used,
+ * so we don't waste IO and cycles loading images the user doesn't see.
+ * It has a list of known problematic images that we aim to reduce to
+ * empty.
+ */
+
+/* A list of images that are loaded at startup but not shown.
+ * List items support the following attributes:
+ *  - file: The location of the loaded image file.
+ *  - hidpi: An alternative hidpi file location for retina screens, if one exists.
+ *           May be the magic string <not loaded> in strange cases where
+ *           only the low-resolution image is loaded but not shown.
+ *  - platforms: An array of the platforms where the issue is occurring.
+ *               Possible values are linux, win, macosx.
+ *  - intermittentNotLoaded: an array of platforms where this image is
+ *                           intermittently not loaded, e.g. because it is
+ *                           loaded during the time we stop recording.
+ *  - intermittentShown: An array of platforms where this image is
+ *                       intermittently shown, even though the list implies
+ *                       it might not be shown.
+ *
+ * PLEASE do not add items to this list.
+ *
+ * PLEASE DO remove items from this list.
+ */
+const knownUnshownImages = [
+  {
+    file: "chrome://global/skin/icons/arrow-left.svg",
+    platforms: ["linux", "win", "macosx"],
+  },
+
+  {
+    file: "chrome://browser/skin/toolbar-drag-indicator.svg",
+    platforms: ["linux", "win", "macosx"],
+  },
+
+  {
+    file: "chrome://global/skin/icons/chevron.svg",
+    platforms: ["win", "linux", "macosx"],
+    intermittentShown: ["win", "linux"],
+  },
+
+  {
+    file: "chrome://browser/skin/window-controls/maximize.svg",
+    platforms: ["win"],
+    // This is to prevent perma-fails in case Windows machines
+    // go back to running tests in non-maximized windows.
+    intermittentShown: ["win"],
+    // This file is not loaded on Windows 7/8.
+    intermittentNotLoaded: ["win"],
+  },
+];
+
+add_task(async function () {
+  if (!AppConstants.DEBUG) {
+    ok(false, "You need to run this test on a debug build.");
+  }
+
+  let startupRecorder =
+    Cc["@mozilla.org/test/startuprecorder;1"].getService().wrappedJSObject;
+  await startupRecorder.done;
+
+  let data = Cu.cloneInto(startupRecorder.data.images, {});
+  let knownImagesForPlatform = knownUnshownImages.filter(el => {
+    return el.platforms.includes(AppConstants.platform);
+  });
+
+  {
+    let results = await PerfTestHelpers.throttledMapPromises(
+      knownImagesForPlatform,
+      async image => ({
+        uri: image.file,
+        exists: await PerfTestHelpers.checkURIExists(image.file),
+      })
+    );
+    for (let { uri, exists } of results) {
+      ok(exists, `Unshown image entry ${uri} must exist`);
+    }
+  }
+
+  let loadedImages = data["image-loading"];
+  let shownImages = data["image-drawing"];
+
+  for (let loaded of loadedImages.values()) {
+    let knownImage = knownImagesForPlatform.find(el => {
+      if (window.devicePixelRatio >= 2 && el.hidpi && el.hidpi == loaded) {
+        return true;
+      }
+      return el.file == loaded;
+    });
+    if (knownImage) {
+      if (
+        !knownImage.intermittentShown ||
+        !knownImage.intermittentShown.includes(AppConstants.platform)
+      ) {
+        todo(
+          shownImages.has(loaded),
+          `Image ${loaded} should not have been shown.`
+        );
+      }
+      continue;
+    }
+    ok(
+      shownImages.has(loaded),
+      `Loaded image ${loaded} should have been shown.`
+    );
+  }
+
+  // Check for known images that are no longer used.
+  for (let item of knownImagesForPlatform) {
+    if (
+      !item.intermittentNotLoaded ||
+      !item.intermittentNotLoaded.includes(AppConstants.platform)
+    ) {
+      if (window.devicePixelRatio >= 2 && item.hidpi) {
+        if (item.hidpi != "<not loaded>") {
+          ok(
+            loadedImages.has(item.hidpi),
+            `Image ${item.hidpi} should have been loaded.`
+          );
+        }
+      } else {
+        ok(
+          loadedImages.has(item.file),
+          `Image ${item.file} should have been loaded.`
+        );
+      }
+    }
+  }
+});