[webauthn] Fix getcredential-extensions WPTs

WPTs testing navigator.credentials.get() webauthn extensions were
expecting errors incorrectly:

* Unrecognized extensions are ignored instead of failing the request
  https://w3c.github.io/webauthn/#sctn-extensions
* null, empty array, and non sensical objects evaluate to dictionaries
  with undefined key values, which means they should also be ignored
  https://heycam.github.io/webidl/#es-dictionary

Fixed: 875444
Change-Id: I5b2cd3d421dc3cddc7010ff3f365314e25cf2a06
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2133159Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Commit-Queue: Nina Satragno <nsatragno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#755874}

third_party/blink/web_tests/external/wpt/webauthn/getcredential-extensions.https-expected.txt

-This is a testharness.js-based test.
-PASS Bad extensions: extensions is string
-FAIL Bad extensions: extensions is null assert_unreached: Should have rejected: Expected bad parameters to fail Reached unreachable code
-FAIL Bad extensions: extensions is empty Array assert_unreached: Should have rejected: Expected bad parameters to fail Reached unreachable code
-FAIL Bad extensions: extensions is empty ArrayBuffer assert_unreached: Should have rejected: Expected bad parameters to fail Reached unreachable code
-FAIL Bad extensions: malformatted JSON assert_unreached: Should have rejected: Expected bad parameters to fail Reached unreachable code
-FAIL Bad extensions: JavaScript object assert_unreached: Should have rejected: Expected bad parameters to fail Reached unreachable code
-FAIL Bad extensions: extension ID too long assert_unreached: Should have rejected: Expected bad parameters to fail Reached unreachable code
-PASS extensions is a nonsensical JSON string
-PASS Clean up the test environment
-Harness: the test ran to completion.
-

third_party/blink/web_tests/external/wpt/webauthn/getcredential-extensions.https.html

@@ -14,46 +14,37 @@
 standardSetup(function() {
     "use strict";
 
+    var credPromise = createCredential();
     var dummyExtension = {
         foo: true,
         bar: "yup"
     };
-    var credPromise = createCredential();
+    var badExtId = {};
+    badExtId[createRandomString(65)] = dummyExtension;
 
     // bad extension values
     new GetCredentialsTest("options.publicKey.extensions", "hi mom")
         .addCredential(credPromise)
         .runTest("Bad extensions: extensions is string", TypeError);
+
+    // empty extensions
     new GetCredentialsTest("options.publicKey.extensions", null)
         .addCredential(credPromise)
-        .runTest("Bad extensions: extensions is null", TypeError);
+        .runTest("extensions is null");
     new GetCredentialsTest("options.publicKey.extensions", [])
         .addCredential(credPromise)
-        .runTest("Bad extensions: extensions is empty Array", TypeError);
+        .runTest("extensions is empty Array");
     new GetCredentialsTest("options.publicKey.extensions", new ArrayBuffer(0))
         .addCredential(credPromise)
-        .runTest("Bad extensions: extensions is empty ArrayBuffer", TypeError);
-    var badJson = '{"foo": true, "bar: "yup"}'; // missing quote after "bar"
-    new GetCredentialsTest("options.publicKey.extensions", {foo: badJson})
-        .addCredential(credPromise)
-        .runTest("Bad extensions: malformatted JSON", TypeError);
+        .runTest("extensions is empty ArrayBuffer");
+
+    // unknown extensions should be ignored
     new GetCredentialsTest("options.publicKey.extensions", {foo: dummyExtension})
         .addCredential(credPromise)
-        .runTest("Bad extensions: JavaScript object", TypeError);
-    var badExtId = {};
-    badExtId[createRandomString(65)] = dummyExtension;
+        .runTest("ignored extension");
     new GetCredentialsTest("options.publicKey.extensions", {badExtId: dummyExtension})
         .addCredential(credPromise)
-        .runTest("Bad extensions: extension ID too long", TypeError);
-
-    // phony extensions
-    // TODO: not sure if this should pass or fail
-    // should be clarified as part of https://github.com/w3c/webauthn/pull/765
-    var randomExtId = {};
-    randomExtId[createRandomString(64)] = dummyExtension;
-    new GetCredentialsTest("options.publicKey.extensions", {foo: JSON.stringify(randomExtId)})
-        .addCredential(credPromise)
-        .runTest("extensions is a nonsensical JSON string");
+        .runTest("extension ID too long");
 
     // TODO
     // defined extensions: