[Web Payment] Very long instrumentId string test.

This patch adds a test for JSON serialization of a very long string
being passed into PaymentRequest API.

Bug: 1110324, 1115091
Change-Id: I7966d71c3752d1e4378a54f534a1915fb8fade39
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2348411
Commit-Queue: Rouslan Solomakhin <rouslan@chromium.org>
Reviewed-by: Nick Burris <nburris@chromium.org>
Cr-Commit-Position: refs/heads/master@{#797165}

third_party/blink/web_tests/external/wpt/payment-request/secure-payment-confirmation.https.html

@@ -174,4 +174,20 @@ test(() => {
     }], details);
   });
 }, 'Timeout longer than 1 hour throws exception.');
+
+test(() => {
+  assert_throws_js(TypeError, () => {
+    new PaymentRequest([{
+      supportedMethods: 'secure-payment-confirmation',
+      data: {
+        action: 'authenticate',
+        // Large instrumentId value.
+        instrumentId: 'x'.repeat(1024 * 1024),
+        networkData: Uint8Array.from('x', c => c.charCodeAt(0)),
+        timeout: 60000,
+        fallbackUrl: 'https://fallback.example/url'
+      },
+    }], details);
+  });
+}, 'Large instrumentId value throws exception.');
 </script>