[PaymentRequest] Implement activationless show

Implement the PaymentRequestAllowOneActivationlessShow feature which
allows one call to PaymentRequest.show() without a user activation.

This mostly reuses the activationless show behaviour implemented for
SPC[1], by adding a separate feature flag that expands the behaviour
to PaymentRequest calls in general.

[1] https://chromium-review.googlesource.com/c/chromium/src/+/4479975

Bug: 1454204
Change-Id: Ia144c4a1b3663e1a7f8a826d789fa05a055a7477
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4672598
Reviewed-by: Stephen McGruer <[email protected]>
Commit-Queue: Nick Burris <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1171890}

payment-request/payment-request-show-method.https.html

@@ -35,12 +35,6 @@
   },
 });
 
-promise_test(async (t) => {
-  const request = new PaymentRequest(defaultMethods, defaultDetails);
-  const acceptPromise = request.show();
-  await promise_rejects_dom(t, "SecurityError", acceptPromise);
-}, `Calling show() without being triggered by user interaction throws`);
-
 promise_test(async (t) => {
   const request = new PaymentRequest(defaultMethods, defaultDetails);
   await promise_rejects_dom(t, "SecurityError", request.show());
@@ -63,11 +57,8 @@
   await test_driver.bless();
   const acceptPromise1 = request1.show();
 
-  // User activation consumed, so...
-  const request2 = new PaymentRequest(defaultMethods, defaultDetails);
-  await promise_rejects_dom(t, "SecurityError", request2.show());
-
   // Payment request already showing, so...
+  const request2 = new PaymentRequest(defaultMethods, defaultDetails);
   await test_driver.bless();
   await promise_rejects_dom(t, "AbortError", request2.show());
 

payment-request/show-consume-activation.https.html

@@ -37,22 +37,16 @@
       promise_test(async t => {
         const pr = new PaymentRequest(defaultMethods, defaultDetails);
 
-        // Not activated by user gesture, so not allowed!
-        await promise_rejects_dom(t, "SecurityError", pr.show());
-
         await test_driver.bless("Calls show() method");
-
-        // Activated by user gesture, so all good.
         const showPromise = pr.show();
 
-        // The activation has been consumed, so calling show() again would require
-        // a new gesture.
-        await promise_rejects_dom(t, "InvalidStateError", pr.show());
+        // The activation has been consumed.
+        assert_false(navigator.userActivation.isActive);
 
         // Abort the payment request
         pr.abort()
         await promise_rejects_dom(t, "AbortError", showPromise);
-      }, "Calling share consumes user activation");
+      }, "Calling show consumes user activation, if present");
     </script>
   </body>
 </html>