1 files changed, 73 insertions, 0 deletions
diff --git a/tools/profiler/tests/browser/browser_test_markers_preferencereads.js b/tools/profiler/tests/browser/browser_test_markers_preferencereads.js
new file mode 100644
index 0000000000..0ae183f874
--- /dev/null
+++ b/tools/profiler/tests/browser/browser_test_markers_preferencereads.js
@@ -0,0 +1,73 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+requestLongerTimeout(10);
+
+const kContentPref = "font.size.variable.x-western";
+
+function countPrefReadsInThread(pref, thread) {
+  let count = 0;
+  for (let payload of getPayloadsOfType(thread, "Preference")) {
+    if (payload.prefName === pref) {
+      count++;
+    }
+  }
+  return count;
+}
+
+async function waitForPaintAfterLoad() {
+  return SpecialPowers.spawn(gBrowser.selectedBrowser, [], () => {
+    return new Promise(function (resolve) {
+      function listener() {
+        if (content.document.readyState == "complete") {
+          content.requestAnimationFrame(() => content.setTimeout(resolve, 0));
+        }
+      }
+      if (content.document.readyState != "complete") {
+        content.document.addEventListener("readystatechange", listener);
+      } else {
+        listener();
+      }
+    });
+  });
+}
+
+/**
+ * Test the Preference Read markers.
+ */
+add_task(async function test_profile_preferencereads_markers() {
+  Assert.ok(
+    !Services.profiler.IsActive(),
+    "The profiler is not currently active"
+  );
+
+  await startProfiler({ features: ["js"] });
+
+  const url = BASE_URL + "single_frame.html";
+  await BrowserTestUtils.withNewTab(url, async contentBrowser => {
+    const contentPid = await SpecialPowers.spawn(
+      contentBrowser,
+      [],
+      () => Services.appinfo.processID
+    );
+
+    await waitForPaintAfterLoad();
+
+    // Ensure we read a pref in the content process.
+    await SpecialPowers.spawn(contentBrowser, [kContentPref], pref => {
+      Services.prefs.getIntPref(pref);
+    });
+
+    // Check that some Preference Read profile markers were generated.
+    {
+      const { contentThread } = await stopProfilerNowAndGetThreads(contentPid);
+
+      Assert.greater(
+        countPrefReadsInThread(kContentPref, contentThread),
+        0,
+        `Preference Read profile markers for ${kContentPref} were recorded.`
+      );
+    }
+  });
+});