PaymentHandler: Implement PaymentInstruments.clear().

third_party/WebKit/LayoutTests/http/tests/payments/payment-instruments.html

Index: third_party/WebKit/LayoutTests/http/tests/payments/payment-instruments.html
diff --git a/third_party/WebKit/LayoutTests/http/tests/payments/payment-instruments.html b/third_party/WebKit/LayoutTests/http/tests/payments/payment-instruments.html
index 8b2c06bf9ea8da198c49ac2140b444fdbe99689e..1e01ca6bc6a570f056af6e306e4d658db93a7645 100644
--- a/third_party/WebKit/LayoutTests/http/tests/payments/payment-instruments.html
+++ b/third_party/WebKit/LayoutTests/http/tests/payments/payment-instruments.html
@@ -161,4 +161,54 @@ promise_test(test => {
       .catch(unreached_rejection(test));
   }, 'PaymentInstruments |keys| method test');
 
+promise_test(test => {
+    var registration;
+    var script_url = 'resources/empty-worker.js';
+    var scope = 'resources/';
+
+    return service_worker_unregister_and_register(test, script_url, scope)
+      .then(r => {
+          registration = r;
+          return wait_for_state(test, registration.installing, 'activated');
+        })
+      .then(state => {
+          assert_equals(state, 'activated');
+          var instruments = [
+            registration.paymentManager.instruments.set(
+              'test_key1',
+              {
+                name: 'Visa ending ****4756',
+                enabledMethods: ['basic-card'],
+                capabilities: {
+                  supportedNetworks: ['visa'],
+                  supportedTypes: ['credit']
+                }
+              }),
+            registration.paymentManager.instruments.set(
+              'test_key2',
+              {
+                name: "My Bob Pay Account: john@example.com",
+                enabledMethods: ["https://bobpay.com/"]
+              })
+          ];
+          return Promise.all(instruments);
+        })
+      .then(result => {
+          assert_array_equals(result, [undefined, undefined]);
+          return registration.paymentManager.instruments.keys();
+        })
+      .then(result => {
+          assert_equals(result.length, 2);
+          return registration.paymentManager.instruments.clear();
+        })
+      .then(result => {
+          assert_equals(result, undefined);
+          return registration.paymentManager.instruments.keys();
+        })
+      .then(result => {
+          assert_equals(result.length, 0);
+        })
+      .catch(unreached_rejection(test));
+  }, 'PaymentInstruments |clear| method test');
+
 </script>