Use GN buildflags and features to configure account consistency

components/signin/core/common/signin_switches.h

Index: components/signin/core/common/signin_switches.h
diff --git a/components/signin/core/common/signin_switches.h b/components/signin/core/common/signin_switches.h
index 213e0e925314708f36e5b4312cf0ac1ce9ae5662..5038a1e4fe362235b1ec4720e9852b4559367f67 100644
--- a/components/signin/core/common/signin_switches.h
+++ b/components/signin/core/common/signin_switches.h
@@ -5,8 +5,7 @@
 #ifndef COMPONENTS_SIGNIN_CORE_COMMON_SIGNIN_SWITCHES_H_
 #define COMPONENTS_SIGNIN_CORE_COMMON_SIGNIN_SWITCHES_H_
 
-#include "base/feature_list.h"
-#include "build/build_config.h"
+#include "components/signin/core/common/signin_features.h"
 
 namespace switches {
 
@@ -23,7 +22,7 @@ extern const char kEnableRefreshTokenAnnotationRequest[];
 extern const char kEnableSigninPromo[];
 extern const char kExtensionsMultiAccount[];
 
-#if !defined(OS_ANDROID) && !defined(OS_IOS)
+#if !BUILDFLAG(ENABLE_MIRROR)
 // Note: Account consistency (Mirror) is already enabled on mobile platforms, so
 // this switch only exist on desktop platforms.
 extern const char kAccountConsistency[];