Refactor sync-specific parts out of SyncNotifier/SyncNotifierObserver

sync/internal_api/public/base/model_type_payload_map.h

Index: sync/internal_api/public/base/model_type_payload_map.h
diff --git a/sync/internal_api/public/base/model_type_payload_map.h b/sync/internal_api/public/base/model_type_payload_map.h
index da708f7c4ec5ab6fc1aad4117d188a2b0207bdd3..443a8225f2233d26c74adee0338846ce2c43e3ec 100644
--- a/sync/internal_api/public/base/model_type_payload_map.h
+++ b/sync/internal_api/public/base/model_type_payload_map.h
@@ -12,6 +12,7 @@
 #include <string>
 
 #include "sync/internal_api/public/base/model_type.h"
+#include "sync/notifier/object_id_payload_map.h"
 
 namespace base {
 class DictionaryValue;
@@ -25,6 +26,12 @@ typedef std::map<ModelType, std::string> ModelTypePayloadMap;
 
 // Helper functions for building ModelTypePayloadMaps.
 
+// Converts between ObjectIdPayloadMaps and ModelTypePayloadMaps.
+ModelTypePayloadMap ObjectIdPayloadMapToModelTypePayloadMap(
+    const ObjectIdPayloadMap& id_payloads);
+ObjectIdPayloadMap ModelTypePayloadMapToObjectIdPayloadMap(
+    const ModelTypePayloadMap& type_payloads);
+
 // Make a TypePayloadMap from all the types in a ModelTypeSet using a
 // default payload.
 ModelTypePayloadMap ModelTypePayloadMapFromEnumSet(