Fire error events for invalid speculation rules tags

This CL introduces error handling for <script type=speculationrules>
with invalid ruleset-level tags. This changes the behavior: previously
we would ignore such tags and preload with the null tag. But now, we
error the entire <script type=speculationrules>, since it is better to
avoid preloading if the web developer is expecting it to get a certain
tag and we cannot fulfill that request.

This matches the spec update at
whatwg/html#11426.

Bug: None
Change-Id: I5d2211510bd4e3a3ecce15010325b411f18fde3a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6746174
Commit-Queue: Domenic Denicola <domenic@chromium.org>
Reviewed-by: Danil Somsikov <dsv@chromium.org>
Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1488633}

Author: domenic

speculation-rules/speculation-tags/resources/speculation-tags-utils.js

@@ -26,6 +26,22 @@
     return type;
   }
 
+  function assertHeaders(headers, expectedTag, preloadingType) {
+    if (expectedTag === undefined) {
+      // If `tag` is invalid, preloading should not be
+      // triggered, and the navigation should fall back to network. Confirm
+      // this behavior by checking the request headers.
+      assert_false(headers.has("sec-purpose"));
+      assert_false(headers.has("sec-speculation-tags"));
+    } else {
+      // Make sure the page is preloaded.
+      assert_equals(
+        headers.get("sec-purpose"),
+        preloadingType === "prefetch" ? "prefetch" : "prefetch;prerender");
+      assert_equals(headers.get("sec-speculation-tags"), expectedTag);
+    }
+  }
+
   function testRulesetTag(tag, expectedTag, description) {
     promise_test(async t => {
         const rcHelper = new RemoteContextHelper();
@@ -35,7 +51,7 @@
         const preloadingType = getPreloadingType();
         const preloadedRC = await referrerRC.helper.createContext({
             executorCreator(url) {
-              return referrerRC.executeScript((preloadingType, tag, url) => {
+              return referrerRC.executeScript((preloadingType, tag, url, expectedTag) => {
                   const script = document.createElement("script");
                   script.type = "speculationrules";
                   script.textContent = JSON.stringify({
@@ -47,20 +63,24 @@
                         }
                       ]
                   });
+
+                  if (expectedTag === undefined) {
+                    return new Promise(resolve => {
+                      script.addEventListener('error', resolve, { once: true });
+                      document.head.append(script);
+                    });
+                  }
+
                   document.head.append(script);
-              }, [preloadingType, tag, url]);
+              }, [preloadingType, tag, url, expectedTag]);
             }, extraConfig
         });
 
         // Navigate to the preloaded page.
         referrerRC.navigateTo(preloadedRC.url);
 
         const headers = await preloadedRC.getRequestHeaders();
-        // Make sure the page is preloaded.
-        assert_equals(
-          headers.get("sec-purpose"),
-          preloadingType === "prefetch" ? "prefetch" : "prefetch;prerender");
-        assert_equals(headers.get("sec-speculation-tags"), expectedTag);
+        assertHeaders(headers, expectedTag, preloadingType);
     }, "Sec-Speculation-Tags [ruleset-based]: " + description);
   }
 
@@ -94,21 +114,7 @@
         referrerRC.navigateTo(preloadedRC.url);
 
         const headers = await preloadedRC.getRequestHeaders();
-
-        if (expectedTag === undefined) {
-          // If `tag` on the rule level is invalid, preloading should not be
-          // triggered, and the navigation should fall back to network. Confirm
-          // this behavior by checking the request headers.
-          assert_false(headers.has("sec-purpose"));
-          assert_false(headers.has("sec-speculation-tags"));
-        } else {
-          // Make sure the page is preloaded.
-          assert_equals(
-            headers.get("sec-purpose"),
-            preloadingType === "prefetch" ? "prefetch" : "prefetch;prerender");
-          assert_equals(headers.get("sec-speculation-tags"), expectedTag);
-        }
-
+        assertHeaders(headers, expectedTag, preloadingType);
     }, "Sec-Speculation-Tags [rule-based]: " + description);
   }
 
@@ -124,7 +130,7 @@
   // Runs the test function for invalid tag cases based on the tag level.
   globalThis.testInvalidTag = (tag, description) => {
     if (getTagLevel() === 'ruleset') {
-      testRulesetTag(tag, 'null', description);
+      testRulesetTag(tag, undefined, description);
     } else {
       // Pass `undefined` to indicate this preloading is expected to fail.
       testRuleTag(tag, undefined, description);