[Payments] Put Web Payments feature on desktop behind flag

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index a54cd2d0a99184ed3ab68f27dd84471cf76e7bf6..80f86efe77eb3ef50c9ebe2aeb39a21c2f36d010 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -98280,6 +98280,7 @@ value.
   <int value="1586022426" label="AutofillCreditCardAssist:enabled"/>
   <int value="1589341623" label="disable-easy-unlock"/>
   <int value="1612446645" label="enable-weak-memorycache"/>
+  <int value="1612871297" label="WebPayments:disabled"/>
   <int value="1612974229" label="allow-insecure-localhost"/>
   <int value="1617187093" label="enable-improved-a2hs"/>
   <int value="1622131033" label="ozone-test-single-overlay-support"/>
@@ -98349,6 +98350,7 @@ value.
   <int value="1889076955" label="disable-app-link"/>
   <int value="1891210939" label="enable-blink-features"/>
   <int value="1892201400" label="enable-password-separated-signin-flow"/>
+  <int value="1893317228" label="WebPayments:enabled"/>
   <int value="1895587769" label="CredentialManagementAPI:disabled"/>
   <int value="1896456311" label="enable-password-save-in-page-navigation"/>
   <int value="1898231011" label="enable-native-notifications"/>