[Sync] Refactor sync datatype error handling.

chrome/browser/prefs/pref_model_associator.h

Index: chrome/browser/prefs/pref_model_associator.h
diff --git a/chrome/browser/prefs/pref_model_associator.h b/chrome/browser/prefs/pref_model_associator.h
index 15031532fdb0437558c83bbe1613a1eea166e3a0..61030db591230b43bdc6b8f238428f76bb7c3ab3 100644
--- a/chrome/browser/prefs/pref_model_associator.h
+++ b/chrome/browser/prefs/pref_model_associator.h
@@ -16,6 +16,7 @@
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/browser/sync/api/syncable_service.h"
 #include "chrome/browser/sync/api/sync_data.h"
+#include "chrome/browser/sync/api/sync_error.h"
 
 namespace sync_pb {
 class PreferenceSpecifics;
@@ -37,12 +38,14 @@ class PrefModelAssociator
 
   // SyncableService implementation.
   virtual SyncDataList GetAllSyncData(syncable::ModelType type) const OVERRIDE;
-  virtual void ProcessSyncChanges(const tracked_objects::Location& from_here,
-                                  const SyncChangeList& change_list) OVERRIDE;
+  virtual bool ProcessSyncChanges(const tracked_objects::Location& from_here,
+                                  const SyncChangeList& change_list,
+                                  SyncError* error) OVERRIDE;
   virtual bool MergeDataAndStartSyncing(
       syncable::ModelType type,
       const SyncDataList& initial_sync_data,
-      SyncChangeProcessor* sync_processor) OVERRIDE;
+      SyncChangeProcessor* sync_processor,
+      SyncError* error) OVERRIDE;
   virtual void StopSyncing(syncable::ModelType type) OVERRIDE;
 
   // Returns the list of preference names that are registered as syncable, and