[Sync] Introduce ModelError for USS error handling.

components/sync/model/model_type_change_processor.h

Index: components/sync/model/model_type_change_processor.h
diff --git a/components/sync/model/model_type_change_processor.h b/components/sync/model/model_type_change_processor.h
index b001832855e7cbb246aaa2463c023b32ab8a4bdb..030e388f8700e856cac61af7da003b1d3983dee2 100644
--- a/components/sync/model/model_type_change_processor.h
+++ b/components/sync/model/model_type_change_processor.h
@@ -8,11 +8,12 @@
 #include <memory>
 #include <string>
 
+#include "base/location.h"
 #include "components/sync/base/model_type.h"
 #include "components/sync/engine/activation_context.h"
 #include "components/sync/model/data_type_error_handler.h"
 #include "components/sync/model/entity_data.h"
-#include "components/sync/model/sync_error_factory.h"
+#include "components/sync/model/model_error.h"
 
 namespace syncer {
 
@@ -23,7 +24,7 @@ class SyncError;
 
 // Interface used by the ModelTypeSyncBridge to inform sync of local
 // changes.
-class ModelTypeChangeProcessor : public SyncErrorFactory {
+class ModelTypeChangeProcessor {
  public:
   typedef base::Callback<void(SyncError, std::unique_ptr<ActivationContext>)>
       StartCallback;
@@ -34,7 +35,7 @@ class ModelTypeChangeProcessor : public SyncErrorFactory {
       ModelTypeSyncBridge* bridge);
 
   ModelTypeChangeProcessor();
-  ~ModelTypeChangeProcessor() override;
+  virtual ~ModelTypeChangeProcessor();
 
   // Inform the processor of a new or updated entity. The |entity_data| param
   // does not need to be fully set, but it should at least have specifics and
@@ -50,8 +51,7 @@ class ModelTypeChangeProcessor : public SyncErrorFactory {
 
   // Accept the initial sync metadata loaded by the bridge. This should be
   // called as soon as the metadata is available to the bridge.
-  virtual void OnMetadataLoaded(SyncError error,
-                                std::unique_ptr<MetadataBatch> batch) = 0;
+  virtual void OnMetadataLoaded(std::unique_ptr<MetadataBatch> batch) = 0;

[skym, 2017/01/09 18:20:28]

Would be nice to talk about about how the bridge needs to call this (unless they
call ReportError) in this file as well, to make it as clear to model type
implementers as possible.

[maxbogue, 2017/01/09 21:29:33]

Done.

 
   // Indicates that sync wants to connect a sync worker to this processor. Once
   // the processor has metadata from the bridge, it will pass the info needed
@@ -71,6 +71,15 @@ class ModelTypeChangeProcessor : public SyncErrorFactory {
   // currently up to date and accurately tracking the model type's data. If
   // false, calls to Put and Delete will no-op and can be omitted by bridge.
   virtual bool IsTrackingMetadata() = 0;
+
+  // Report an error in the model to sync. Must be called for any error that
+  // happens outside the bridge methods that synchronously return an error.
+  // This will result in disable being called asynchronously by the bridge.
+  virtual void ReportError(const ModelError& error) = 0;

[skym, 2017/01/09 18:20:28]

Same as above.

[maxbogue, 2017/01/09 21:29:33]

Done.

+
+  // A convenience form of the above.
+  virtual void ReportError(const tracked_objects::Location& location,
+                           const std::string& message) = 0;
 };
 
 }  // namespace syncer