[Sync] Add favicon datatype proto support

sync/protocol/proto_enum_conversions.h

Index: sync/protocol/proto_enum_conversions.h
diff --git a/sync/protocol/proto_enum_conversions.h b/sync/protocol/proto_enum_conversions.h
index a0278589b0bd76208dfdcada9f85e724a45994a1..125add937a7eaa55613cb878b2bf05f629a64b9b 100644
--- a/sync/protocol/proto_enum_conversions.h
+++ b/sync/protocol/proto_enum_conversions.h
@@ -9,6 +9,7 @@
 
 #include "sync/base/sync_export.h"
 #include "sync/protocol/client_debug_info.pb.h"
+#include "sync/protocol/favicon_specifics.pb.h"
 #include "sync/protocol/session_specifics.pb.h"
 #include "sync/protocol/sync.pb.h"
 
@@ -48,6 +49,9 @@ const char* GetDeviceTypeString(
 const char* GetFaviconTypeString(
     sync_pb::SessionTab::FaviconType favicon_type);
 
+const char* GetIconTypeString(
+    sync_pb::FaviconData::IconType icon_type);
+
 const char* PassphraseTypeString(
     sync_pb::NigoriSpecifics::PassphraseType type);