chrome/browser/payments: Use BUILDFLAG for OS checking

Use BUILDFLAG(IS_XXX) instead of defined(OS_XXX).

Generated by `os_buildflag_migration.py` (https://crrev.com/c/3311983).

[email protected]

Bug: 1234043
Test: No functionality change
Change-Id: Ie53fd1d3a867557986f3be5f2c23781dccc6a895
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3392807
Commit-Queue: Xiaohan Wang <[email protected]>
Reviewed-by: Nico Weber <[email protected]>
Commit-Queue: Nico Weber <[email protected]>
Cr-Commit-Position: refs/heads/main@{#959749}
diff --git a/chrome/browser/payments/abort_payment_handler_browsertest.cc b/chrome/browser/payments/abort_payment_handler_browsertest.cc
index a6c8104..a602293 100644
--- a/chrome/browser/payments/abort_payment_handler_browsertest.cc
+++ b/chrome/browser/payments/abort_payment_handler_browsertest.cc
@@ -16,7 +16,7 @@
 class AbortPaymentHandlerTest : public PaymentRequestPlatformBrowserTestBase {};
 
 // TODO(crbug.com/1129578): fix flakiness and reenable
-#if defined(OS_MAC)
+#if BUILDFLAG(IS_MAC)
 #define MAYBE_CanAbortInvokedInstalledPaymentHandler \
   DISABLED_CanAbortInvokedInstalledPaymentHandler
 #else