[ExpandablePaymentHandler] Disable flaky test

Because ExpandablePaymentHandlerBrowserTest.CancelPayment is flaky,
disable the test before we find the cause.

Bug: 1045274

Change-Id: Iaa253bccc7edc8141061dd8df5aa921ca1bc89bb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2020570Reviewed-by: Liquan (Max) Gu <maxlg@chromium.org>
Reviewed-by: Rouslan Solomakhin <rouslan@chromium.org>
Commit-Queue: Liquan (Max) Gu <maxlg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#735302}

chrome/browser/payments/expandable_payment_handler_browsertest.cc

@@ -64,7 +64,7 @@ IN_PROC_BROWSER_TEST_F(ExpandablePaymentHandlerBrowserTest, ConfirmPayment) {
   EXPECT_EQ("success", content::EvalJs(GetActiveWebContents(), "getResult()"));
 }
 
-IN_PROC_BROWSER_TEST_F(ExpandablePaymentHandlerBrowserTest, CancelPayment) {
+IN_PROC_BROWSER_TEST_F(ExpandablePaymentHandlerBrowserTest, DISABLED_CancelPayment) {
   std::string expected = "success";
   EXPECT_EQ(expected, content::EvalJs(GetActiveWebContents(), "install()"));
   EXPECT_EQ("app_is_ready", content::EvalJs(GetActiveWebContents(),