Recover the browser session on test timeout to keep running subsequent tests

When a reftest hangs and trips the per-browser timeout, the session was
closed, which left every remaining task in the per-browserType queue with
no consumer and effectively skipped the rest of the manifest. Instead,
mark the in-flight task(s) as failed, reload the page so the driver can
reconnect and request the next task, and only fall back to closing the
session if the reload itself fails.

test/test.mjs

@@ -423,15 +423,38 @@ async function startRefTest(masterMode, showRefImages) {
   checkRefsTmp();
 }
 
-function handleSessionTimeout(session) {
-  if (session.closed) {
+async function handleSessionTimeout(session) {
+  if (session.closed || session.recovering) {
     return;
   }
+  const inflightIds = Object.keys(session.tasks);
+  const suffix = inflightIds.length > 0 ? ` (${inflightIds.join(", ")})` : "";
   console.log(
-    `${TEST_UNEXPECTED_FAIL} | test failed ${session.name} has not responded in ${browserTimeout}s`
+    `${TEST_UNEXPECTED_FAIL} | test failed ${session.name} has not responded in ${browserTimeout}s${suffix}`
   );
   session.numErrors += session.remaining;
   session.remaining = 0;
+  session.taskResults = {};
+  session.tasks = {};
+
+  monitorBrowserTimeout(session, null);
+  if (session.page) {
+    session.recovering = true;
+    try {
+      await session.page.reload({
+        timeout: browserTimeout * 1000,
+        waitUntil: "domcontentloaded",
+      });
+      session.recovering = false;
+      monitorBrowserTimeout(session, handleSessionTimeout);
+      return;
+    } catch (err) {
+      console.log(
+        `Failed to reload ${session.name} after timeout: ${err.message}`
+      );
+      session.recovering = false;
+    }
+  }
   closeSession(session.name);
 }
 
@@ -768,9 +791,15 @@ async function handleWsBinaryResult(data) {
   const { browser, id, round, page, failure, lastPageNum, numberOfTasks } =
     meta;
   const session = getSession(browser);
+  if (!session || session.closed) {
+    return;
+  }
   monitorBrowserTimeout(session, handleSessionTimeout);
 
   const taskResults = session.taskResults[id];
+  if (!taskResults) {
+    return;
+  }
   if (!taskResults[round]) {
     taskResults[round] = [];
   }