[Sync] Refactor sync datatype error handling.

chrome/browser/sync/api/sync_change_processor.h

Index: chrome/browser/sync/api/sync_change_processor.h
diff --git a/chrome/browser/sync/api/sync_change_processor.h b/chrome/browser/sync/api/sync_change_processor.h
index 80be610ab5b4902bf0e1f6021108af4f1f38f2e2..6098693d5da9c5033eca836d747affed019dc60d 100644
--- a/chrome/browser/sync/api/sync_change_processor.h
+++ b/chrome/browser/sync/api/sync_change_processor.h
@@ -9,6 +9,7 @@
 #include <vector>
 
 class SyncChange;
+class SyncError;
 
 namespace tracked_objects {
 class Location;
@@ -20,8 +21,14 @@ typedef std::vector<SyncChange> SyncChangeList;
 class SyncChangeProcessor {
  public:
   // Process a list of SyncChanges.
-  virtual void ProcessSyncChanges(const tracked_objects::Location& from_here,
-                                  const SyncChangeList& change_list) = 0;
+  // Returns: false if an error occured, true otherwise.
+  // Inputs:
+  //   |from_here|: allows tracking of where sync changes originate.
+  //   |change_list|: is the list of sync changes in need of processing.
+  //   |error|: if an error occurred, the error tracking information.
+  virtual bool ProcessSyncChanges(const tracked_objects::Location& from_here,
+                                  const SyncChangeList& change_list,
+                                  SyncError* error) = 0;
  protected:
   virtual ~SyncChangeProcessor();
 };