[Sync] Refactor sync datatype error handling.

chrome/browser/sync/api/syncable_service.h

Index: chrome/browser/sync/api/syncable_service.h
diff --git a/chrome/browser/sync/api/syncable_service.h b/chrome/browser/sync/api/syncable_service.h
index 3c409759df863acae36d1ee2e590e39c148cb081..56c11650de1abcc715657d7d4b6be73a147da832 100644
--- a/chrome/browser/sync/api/syncable_service.h
+++ b/chrome/browser/sync/api/syncable_service.h
@@ -14,6 +14,7 @@
 #include "chrome/browser/sync/api/sync_data.h"
 
 class SyncData;
+class SyncError;
 
 typedef std::vector<SyncData> SyncDataList;
 
@@ -25,10 +26,14 @@ class SyncableService : public SyncChangeProcessor {
   // two. After this, the SyncableService's local data should match the server
   // data, and the service should be ready to receive and process any further
   // SyncChange's as they occur.
+  // Returns: false if an error occurred (and |error| will be reset to describe
+  //                the error).
+  //          true otherwise.
   virtual bool MergeDataAndStartSyncing(
       syncable::ModelType type,
       const SyncDataList& initial_sync_data,
-      SyncChangeProcessor* sync_processor) = 0;
+      SyncChangeProcessor* sync_processor,
+      SyncError* error) = 0;
 
   // Stop syncing the specified type and reset state.
   virtual void StopSyncing(syncable::ModelType type) = 0;
@@ -40,9 +45,13 @@ class SyncableService : public SyncChangeProcessor {
 
   // SyncChangeProcessor interface.
   // Process a list of new SyncChanges and update the local data as necessary.
-  virtual void ProcessSyncChanges(
+  // Returns: false if an error occurred (and |error| will be reset to describe
+  //                the error).
+  //          true otherwise.
+  virtual bool ProcessSyncChanges(
       const tracked_objects::Location& from_here,
-      const SyncChangeList& change_list) OVERRIDE = 0;
+      const SyncChangeList& change_list,
+      SyncError* error) OVERRIDE = 0;
 
  protected:
   virtual ~SyncableService();