Mark a test in PaymentRequestDynamicShippingSingleAddressTest flaky

This patch adds a FlakyTest annotation for testAddInvalidAddressAndCancel

BUG=673136
TBR=dfalcantara

Review-Url: https://codereview.chromium.org/2566923003
Cr-Commit-Position: refs/heads/master@{#437831}

chrome/android/javatests/src/org/chromium/chrome/browser/payments/PaymentRequestDynamicShippingSingleAddressTest.java

@@ -68,7 +68,7 @@ public class PaymentRequestDynamicShippingSingleAddressTest extends PaymentReque
     }
 
     /** Attempt to add an invalid address and cancel the transaction. */
-    @MediumTest
+    @FlakyTest(message = "crbug.com/673136")
     @Feature({"Payments"})
     public void testAddInvalidAddressAndCancel()
             throws InterruptedException, ExecutionException, TimeoutException {