[renderblocking] Add a new class to get link preload finish callbacks

In the existing code, LinkLoader is the only class that receives callbacks when a link preload/modulepreload finishes. This patch moves the logic into a new class PendingLinkPreload. The purposes are: 1. The new class will allow link header preloads to also receive callbacks when finishing, so that we can enable render-blocking on link headers. This will be implemented in crrev.com/c/3551557. 2. Moves the place where render-blocking starts from LinkLoader::LoadLink() (which may or may not actually start a fetch) to PreloadHelper::Preload/ModulePreloadIfNeeded(), right before where we actually start the preload. This fixes a bug that an invalid preload link with `blocking="render"` infinitely blocks rendering, for which we don't start a fetch so their finish callbacks will never be fired, which means the old implementation never unblocks rendering on them. This is verified by the new test invalid-render-blocking-preload-link.html. The most important code changes to review are in: - link_loader.h/cc - pending_link_preload.h/cc - preload_helper.h/cc Bug: 1271296 Change-Id: I8f183b2b0f26c550e76319cda70d890b1d52f247 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3547303 Reviewed-by: Mason Freed <masonf@chromium.org> Reviewed-by: Joey Arhar <jarhar@chromium.org> Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org> Cr-Commit-Position: refs/heads/main@{#987234}
web-platform-tests · Mar 30, 2022 · 2d8c118 · 2d8c118
1 parent bef65dc
commit 2d8c118
Showing 1 changed file with 15 additions and 0 deletions.
diff --git a/html/dom/render-blocking/invalid-render-blocking-preload-link.html b/html/dom/render-blocking/invalid-render-blocking-preload-link.html
@@ -0,0 +1,15 @@
+<!DOCTYPE html>
+<title>An invalid preload link should not block rendering</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/preload/resources/preload_helper.js"></script>
+<link rel="preload" as="invalid" blocking="render"
+      href="/fonts/Ahem.ttf?pipe=trickle(d1)">
+<script>
+promise_test(async () => {
+  // requestAnimationFrame() should be eventually run, and the invalid preload
+  // link should not be loaded.
+  await new Promise(resolve => requestAnimationFrame(resolve));
+  verifyNumberOfResourceTimingEntries('/fonts/Ahem.ttf?pipe=trickle(d1)', 0);
+});
+</script>