1 files changed, 60 insertions, 0 deletions
diff --git a/js/xpconnect/tests/browser/browser_parent_process_hang_telemetry.js b/js/xpconnect/tests/browser/browser_parent_process_hang_telemetry.js
new file mode 100644
index 0000000000..f9b325c216
--- /dev/null
+++ b/js/xpconnect/tests/browser/browser_parent_process_hang_telemetry.js
@@ -0,0 +1,60 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/**
+ * Check that we record hangs in the parent process in telemetry events.
+ * This test would be an xpcshell test except xpcshell does not think
+ * it is running e10s (see bug 1568333).
+ */
+add_task(async function test_browser_hang() {
+  // Trip some testing code to ensure we can test this. Sadly, this is a magic
+  // number corresponding to code in XPCJSContext.cpp
+  await SpecialPowers.pushPrefEnv({
+    set: [["dom.max_chrome_script_run_time", 2]],
+  });
+  await SpecialPowers.promiseTimeout(0);
+
+  // Hang for 1.2 seconds.
+  let now = Date.now();
+  let i = 0;
+  info("Start loop");
+  while (Date.now() - now < 2500) {
+    // The system clock can go backwards. Don't time out the test:
+    if (Date.now() - now < 0) {
+      info("Yikes, the system clock changed while running this test.");
+      now = Date.now();
+    }
+    i++;
+  }
+  let duration = (Date.now() - now) / 1000;
+  info("Looped " + i + " iterations.");
+
+  let events;
+  await TestUtils.waitForCondition(() => {
+    events = Services.telemetry.snapshotEvents(
+      Ci.nsITelemetry.DATASET_ALL_CHANNELS,
+      false
+    );
+    return events.parent?.some(e => e[1] == "slow_script_warning");
+  }, "Should find an event after doing this.").catch(e => ok(false, e));
+  events = events.parent || [];
+  let event = events.find(e => e[1] == "slow_script_warning");
+  ok(event, "Should have registered an event.");
+  if (event) {
+    is(event[3], "browser", "Should register as browser hang.");
+    let args = event[5];
+    is(args.uri_type, "browser", "Should register browser uri type.");
+    Assert.greater(
+      duration + 1,
+      parseFloat(args.hang_duration),
+      "hang duration should not exaggerate."
+    );
+    Assert.less(
+      duration - 1,
+      parseFloat(args.hang_duration),
+      "hang duration should not undersell."
+    );
+  }
+});