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

components/sync/model/entity_change.h

Index: components/sync/model/entity_change.h
diff --git a/components/sync/model/entity_change.h b/components/sync/model/entity_change.h
index 408f370d54196da122bbf7feb691ded0c8e1d48c..65349fb6bcac27387a7b1e2246b3e1873b5325c4 100644
--- a/components/sync/model/entity_change.h
+++ b/components/sync/model/entity_change.h
@@ -28,6 +28,10 @@ class EntityChange {
   std::string storage_key() const { return storage_key_; }
   ChangeType type() const { return type_; }
   const EntityData& data() const { return data_.value(); }
+  // TODO(pavely): data_ptr() is added temporarily to support converting
+  // ModelTypeSyncBridge::MergeSyncData from map to change list. Should be
+  // removed as part of crbug.com/719570.
+  const EntityDataPtr& data_ptr() const { return data_; }
 
  private:
   EntityChange(const std::string& storage_key,