[SyncFS] Add UMAs to track syncfs usage

chrome/browser/sync_file_system/remote_file_sync_service.h

Index: chrome/browser/sync_file_system/remote_file_sync_service.h
diff --git a/chrome/browser/sync_file_system/remote_file_sync_service.h b/chrome/browser/sync_file_system/remote_file_sync_service.h
index 22cec45bc8e23c1d5df9057740035a2a9dbfbae2..4d0245887a294e33c697f50cb4f2c4f4ac2b4b0c 100644
--- a/chrome/browser/sync_file_system/remote_file_sync_service.h
+++ b/chrome/browser/sync_file_system/remote_file_sync_service.h
@@ -41,7 +41,7 @@ enum RemoteServiceState {
   // Remote service is up and running, or has not seen any errors yet.
   // The consumer of this service can make new requests while the
   // service is in this state.
-  REMOTE_SERVICE_OK,
+  REMOTE_SERVICE_OK = 0,
 
   // Remote service is temporarily unavailable due to network,
   // authentication or some other temporary failure.
@@ -63,6 +63,8 @@ enum RemoteServiceState {
   // Any new requests will immediately fail when the service is in
   // this state.
   REMOTE_SERVICE_DISABLED,
+
+  REMOTE_SERVICE_STATE_MAX,
 };
 
 // This class represents a backing service of the sync filesystem.