[Sync] Implement support for updating storage key for new entities

components/sync/model_impl/shared_model_type_processor.h

Index: components/sync/model_impl/shared_model_type_processor.h
diff --git a/components/sync/model_impl/shared_model_type_processor.h b/components/sync/model_impl/shared_model_type_processor.h
index 62c136fa5b786369807c7c85b6f2ad9f4d8626fc..306a7c10c124bfdfaf5f58f689eff1b608465109 100644
--- a/components/sync/model_impl/shared_model_type_processor.h
+++ b/components/sync/model_impl/shared_model_type_processor.h
@@ -57,8 +57,8 @@ class SharedModelTypeProcessor : public ModelTypeProcessor,
            MetadataChangeList* metadata_change_list) override;
   void Delete(const std::string& storage_key,
               MetadataChangeList* metadata_change_list) override;
-  void UpdateStorageKey(const std::string& old_storage_key,
-                        const std::string& new_storage_key,
+  void UpdateStorageKey(const EntityData& entity_data,
+                        const std::string& storage_key,
                         MetadataChangeList* metadata_change_list) override;
   void ModelReadyToSync(std::unique_ptr<MetadataBatch> batch) override;
   void OnSyncStarting(const ModelErrorHandler& error_handler,
@@ -146,6 +146,9 @@ class SharedModelTypeProcessor : public ModelTypeProcessor,
   // Version of the above that generates a tag for |data|.
   ProcessorEntityTracker* CreateEntity(const EntityData& data);
 
+  // Returns true if all processor entity trackers have non-empty storage keys.
+  bool AllStorageKeysPopulated() const;
+
   /////////////////////
   // Processor state //
   /////////////////////
@@ -209,6 +212,10 @@ class SharedModelTypeProcessor : public ModelTypeProcessor,
   // define and can understand more easily. All of the sync machinery wants to
   // use client tag hash. This mapping allows us to convert from storage key to
   // client tag hash. The other direction can use |entities_|.
+  // Entity is not included in this map when the bridge doesn't support

[skym, 2017/05/31 19:53:12]

This comment seems misleading.  They're only not included in here temporarily,
right?

[pavely, 2017/06/02 18:23:46]

Is this one better?

[skym, 2017/06/02 23:07:56]

Yes! Thanks.

+  // GetStorageKey(). In this case the bridge is responsible for calling
+  // UpdateStorageKey() as part of processing entity in
+  // MergeSyncData/ApplySyncChanges.
   std::map<std::string, std::string> storage_key_to_tag_hash_;
 
   // WeakPtrFactory for this processor which will be sent to sync thread.