smbprovider: Generalize operation errors

This change adds more generic Start/Continue operation errors and method
constants for Start/ContinueReadDirectory.

BUG=chromium:757625
TEST=emerges
Change-Id: Ic73faa628e3e825190e4d46ddaa3d1f671054edd
Reviewed-on: https://chromium-review.googlesource.com/1226156
Commit-Ready: Bailey Berro <baileyberro@chromium.org>
Tested-by: Bailey Berro <baileyberro@chromium.org>
Reviewed-by: Zentaro Kavanagh <zentaro@chromium.org>
diff --git a/dbus/smbprovider/dbus-constants.h b/dbus/smbprovider/dbus-constants.h
index 537ddad..b5cb760 100644
--- a/dbus/smbprovider/dbus-constants.h
+++ b/dbus/smbprovider/dbus-constants.h
@@ -34,6 +34,8 @@
 const char kParseNetBiosPacketMethod[] = "ParseNetBiosPacket";
 const char kStartCopyMethod[] = "StartCopy";
 const char kContinueCopyMethod[] = "ContinueCopy";
+const char kStartReadDirectoryMethod[] = "StartReadDirectory";
+const char kContinueReadDirectoryMethod[] = "ContinueReadDirectory";
 
 }  // namespace smbprovider
 
diff --git a/dbus/smbprovider/directory_entry.proto b/dbus/smbprovider/directory_entry.proto
index feeccc4..6a6ffa5 100644
--- a/dbus/smbprovider/directory_entry.proto
+++ b/dbus/smbprovider/directory_entry.proto
@@ -39,6 +39,8 @@
   ERROR_COPY_PENDING = 51;
   ERROR_COPY_FAILED = 52;
   ERROR_SMB1_UNSUPPORTED = 53;
+  ERROR_OPERATION_PENDING = 54;
+  ERROR_OPERATION_FAILED = 55;
 }
 
 message DirectoryEntryProto {