arc: Prepare ArcAuthEndpoint flag for finch experiment.

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 4e1dd217e61e72b9e2e5c2caa24e46af81b4cdd4..5b68d6357495305424f156f9b45c7ea6177e1e8e 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -90830,6 +90830,7 @@ value.
   <int value="-1559789642" label="RunAllFlashInAllowMode:enabled"/>
   <int value="-1553477903" label="ash-disable-text-filtering-in-overview-mode"/>
   <int value="-1546903171" label="enable-touch-drag-drop"/>
+  <int value="-1544248549" label="ArcUseAuthEndpoint:enabled"/>
   <int value="-1543316040"
       label="DisplayPersistenceToggleInPermissionPrompts:disabled"/>
   <int value="-1536293422" label="SharedArrayBuffer:enabled"/>
@@ -90951,6 +90952,7 @@ value.
   <int value="-979034258" label="disable-ntp-other-sessions-menu"/>
   <int value="-978700508" label="disable-simplified-fullscreen-ui"/>
   <int value="-977476498" label="disable-eol-notification"/>
+  <int value="-972737445" label="ArcUseAuthEndpoint:disabled"/>
   <int value="-972425050" label="gesture-editing"/>
   <int value="-968010468" label="SharedArrayBuffer:disabled"/>
   <int value="-964676765" label="enable-accelerated-mjpeg-decode"/>
@@ -91440,7 +91442,6 @@ value.
   <int value="1421620678" label="simple-clear-browsing-data-support-string"/>
   <int value="1442798825" label="enable-quic"/>
   <int value="1454363479" label="disable-storage-manager"/>
-  <int value="1458583431" label="arc-use-auth-endpoint"/>
   <int value="1459529277" label="disable-text-input-focus-manager"/>
   <int value="1460958818" label="NTPForeignSessionsSuggestions:enabled"/>
   <int value="1465624446" label="disable-zero-copy"/>