[Sync] Add favicon datatype proto support

sync/protocol/proto_value_conversions.h

Index: sync/protocol/proto_value_conversions.h
diff --git a/sync/protocol/proto_value_conversions.h b/sync/protocol/proto_value_conversions.h
index 26eadbd0d31da0fdb3c3c928f8e3f63cdc3b59c3..3eca05d6877d8918bf6c0980c07a05470ec68272 100644
--- a/sync/protocol/proto_value_conversions.h
+++ b/sync/protocol/proto_value_conversions.h
@@ -38,6 +38,7 @@ class ExtensionSettingSpecifics;
 class ExtensionSettingSpecifics;
 class ExtensionSpecifics;
 class ExtensionSpecifics;
+class FaviconSpecifics;
 class GlobalIdDirective;
 class HistoryDeleteDirectiveSpecifics;
 class KeystoreEncryptionFlagsSpecifics;
@@ -156,6 +157,9 @@ SYNC_EXPORT_PRIVATE base::DictionaryValue* ExtensionSettingSpecificsToValue(
 SYNC_EXPORT_PRIVATE base::DictionaryValue* ExtensionSpecificsToValue(
     const sync_pb::ExtensionSpecifics& extension_specifics);
 
+SYNC_EXPORT_PRIVATE base::DictionaryValue* FaviconSpecificsToValue(
+    const sync_pb::FaviconSpecifics& favicon_specifics);
+
 SYNC_EXPORT base::DictionaryValue* HistoryDeleteDirectiveSpecificsToValue(
     const sync_pb::HistoryDeleteDirectiveSpecifics&
         history_delete_directive_specifics);