idlharness test fixups (#23416)

Follow-ups from https://github.com/web-platform-tests/wpt/pull/23397#issuecomment-624203679

Co-authored-by: Domenic Denicola <d@domenic.me>
diff --git a/FileAPI/idlharness.html b/FileAPI/idlharness.html
index db6592e..5e0a43f 100644
--- a/FileAPI/idlharness.html
+++ b/FileAPI/idlharness.html
@@ -26,9 +26,6 @@
         ['FileAPI'],
         ['dom', 'html', 'url'],
         idl_array => {
-          idl_array.add_untested_idls(
-            "[Exposed=(Window,Worker)] interface ArrayBuffer {};"
-          );
           idl_array.add_objects({
             Blob: ['new Blob(["TEST"])'],
             File: ['new File(["myFileBits"], "myFileName")'],
diff --git a/FileAPI/idlharness.worker.js b/FileAPI/idlharness.worker.js
index 5bf82e0..786b7e4 100644
--- a/FileAPI/idlharness.worker.js
+++ b/FileAPI/idlharness.worker.js
@@ -9,7 +9,6 @@
   ['FileAPI'],
   ['dom', 'html', 'url'],
   idl_array => {
-    idl_array.add_untested_idls("[Exposed=(Window,Worker)] interface ArrayBuffer {};");
     idl_array.add_objects({
       Blob: ['new Blob(["TEST"])'],
       File: ['new File(["myFileBits"], "myFileName")'],
diff --git a/interfaces/trusted-types.tentative.idl b/interfaces/trusted-types.tentative.idl
index 18a8bfe..f2318d6 100644
--- a/interfaces/trusted-types.tentative.idl
+++ b/interfaces/trusted-types.tentative.idl
@@ -29,7 +29,7 @@
   Exposed=(Window, Worker),
   SecureContext
 ] interface TrustedTypePolicyFactory {
-    TrustedTypePolicy createPolicy(DOMString policyName, TrustedTypePolicyOptions policyOptions);
+    TrustedTypePolicy createPolicy(DOMString policyName, optional TrustedTypePolicyOptions policyOptions = {});
     // All the policy object names that have been created
 };
 
diff --git a/wasm/jsapi/idlharness.any.js b/wasm/jsapi/idlharness.any.js
index 25298d3..a2de9de 100644
--- a/wasm/jsapi/idlharness.any.js
+++ b/wasm/jsapi/idlharness.any.js
@@ -17,9 +17,6 @@
     except: ['CompileError', 'LinkError', 'RuntimeError']
   });
 
-  // https://github.com/web-platform-tests/wpt/issues/12850
-  idl_array.add_untested_idls('[Exposed=(Window,Worker)] interface ArrayBuffer {};');
-
   // Ignored errors are surfaced in idlharness.js's test_object below.
   try {
     self.memory = new WebAssembly.Memory({initial: 1024});