[Sync] Move ConfigureDataTypes logic into DataTypeManagerImpl.

components/sync/driver/data_type_manager_impl.h

Index: components/sync/driver/data_type_manager_impl.h
diff --git a/components/sync/driver/data_type_manager_impl.h b/components/sync/driver/data_type_manager_impl.h
index dd6f3ce45280171ce066d0f54b1c812986047be7..63fa3b8bcada870c262500ff4debc27a083ef399 100644
--- a/components/sync/driver/data_type_manager_impl.h
+++ b/components/sync/driver/data_type_manager_impl.h
@@ -72,7 +72,30 @@ class DataTypeManagerImpl : public DataTypeManager,
     return &model_association_manager_;
   }
 
+ protected:
+  // Returns the priority types (control + priority user types).
+  // Virtual for overriding during tests.
+  virtual ModelTypeSet GetPriorityTypes() const;
+
+  // The set of types that are enabled inside the sync engine.
+  ModelTypeSet engine_types_;

[pavely, 2017/01/05 21:32:19]

This set represents types which don't need to be downloaded as part of
configuration. Sync data for these types is locally available. Alternative names
could be:
- types_with_local_data_
- locally_available_types_

[maxbogue, 2017/01/06 18:55:58]

I've gone with downloaded_types_, which I think is the most concise and clear.
It's easy to change though, so let me know if you disagree!

+
  private:
+  enum DataTypeConfigState {
+    CONFIGURE_ACTIVE,    // Actively being configured. Data of such types
+                         // will be downloaded if not present locally.
+    CONFIGURE_INACTIVE,  // Already configured or to be configured in future.
+                         // Data of such types is left as it is, no
+                         // downloading or purging.
+    CONFIGURE_CLEAN,     // Actively being configured but requiring unapply
+                         // and GetUpdates first (e.g. for persistence errors).
+    DISABLED,            // Not syncing. Disabled by user.
+    FATAL,               // Not syncing due to unrecoverable error.
+    CRYPTO,              // Not syncing due to a cryptographer error.
+    UNREADY,             // Not syncing due to transient error.
+  };
+  using DataTypeConfigStateMap = std::map<ModelType, DataTypeConfigState>;
+
   // Helper enum for identifying which types within a priority group to
   // associate.
   enum AssociationGroup {
@@ -87,15 +110,24 @@ class DataTypeManagerImpl : public DataTypeManager,
     UNREADY_AT_CONFIG,
   };
 
-  friend class TestDataTypeManager;
+  // Return model types in |state_map| that match |state|.
+  static ModelTypeSet GetDataTypesInState(
+      DataTypeConfigState state,
+      const DataTypeConfigStateMap& state_map);
+
+  // Set state of |types| in |state_map| to |state|.
+  static void SetDataTypesState(DataTypeConfigState state,
+                                ModelTypeSet types,
+                                DataTypeConfigStateMap* state_map);
+
+  // Perform a configuration using our local information and inform the
+  // configurer of the result. Returns the set of types that were already ready
+  // for association.
+  ModelTypeSet ConfigureDataTypes();

[pavely, 2017/01/05 21:32:19]

Name "ConfigureDataTypes" can be confused with Configure() and ConfigureImpl().
At the same time this function performs two tasks:
- Translate from local state to configuration parameters
- Invoke configurer

Maybe you could refactor it into PrepareConfigurationParameters which populates
parameters and then call configurer directly from StartNextDownload.

[maxbogue, 2017/01/06 18:55:58]

Done.

 
   // Abort configuration and stop all data types due to configuration errors.
   void Abort(ConfigureStatus status);
 
-  // Returns the priority types (control + priority user types).
-  // Virtual for overriding during tests.
-  virtual ModelTypeSet GetPriorityTypes() const;
-
   // Divide |types| into sets by their priorities and return the sets from
   // high priority to low priority.
   TypeSetPriorityList PrioritizeTypes(const ModelTypeSet& types);
@@ -123,7 +155,7 @@ class DataTypeManagerImpl : public DataTypeManager,
   // Calls data type controllers of requested types to register with backend.
   void RegisterTypesWithBackend();
 
-  ModelTypeConfigurer::DataTypeConfigStateMap BuildDataTypeConfigStateMap(
+  DataTypeConfigStateMap BuildDataTypeConfigStateMap(
       const ModelTypeSet& types_being_configured) const;
 
   // Start download of next set of types in |download_types_queue_| (if