[Sync] Have configuration specify which datatypes are ready to sync

In preparation for performing model association while other types are downloading,
the BackendDataTypeConfigurer::ConfigureDataTypes method will now return those
types that are ready to sync without further intervention from sync. These are the
types that were already syncing previously, and therefore don't need to be
downloaded or purged.

A followup patch will add the association logic and tests.

BUG=477063

Review URL: https://codereview.chromium.org/1081413003

Cr-Commit-Position: refs/heads/master@{#325582}

chrome/browser/sync/glue/sync_backend_host.h

@@ -133,7 +133,10 @@ class SyncBackendHost : public sync_driver::BackendDataTypeConfigurer {
   // The ready_task will be run when configuration is done with the
   // set of all types that failed configuration (i.e., if its argument
   // is non-empty, then an error was encountered).
-  void ConfigureDataTypes(
+  // Returns the set of types that are ready to start without needing any
+  // further sync activity.
+  // BackendDataTypeConfigurer implementation.
+  syncer::ModelTypeSet ConfigureDataTypes(
       syncer::ConfigureReason reason,
       const DataTypeConfigStateMap& config_state_map,
       const base::Callback<void(syncer::ModelTypeSet, syncer::ModelTypeSet)>&

chrome/browser/sync/glue/sync_backend_host_impl.cc

@@ -324,11 +324,11 @@ void SyncBackendHostImpl::UnregisterInvalidationIds() {
   }
 }
 
-void SyncBackendHostImpl::ConfigureDataTypes(
+syncer::ModelTypeSet SyncBackendHostImpl::ConfigureDataTypes(
     syncer::ConfigureReason reason,
     const DataTypeConfigStateMap& config_state_map,
-    const base::Callback<void(syncer::ModelTypeSet,
-                              syncer::ModelTypeSet)>& ready_task,
+    const base::Callback<void(syncer::ModelTypeSet, syncer::ModelTypeSet)>&
+        ready_task,
     const base::Callback<void()>& retry_callback) {
   // Only one configure is allowed at a time.  This is guaranteed by our
   // callers.  The SyncBackendHostImpl requests one configure as the backend is
@@ -445,6 +445,12 @@ void SyncBackendHostImpl::ConfigureDataTypes(
                          routing_info,
                          ready_task,
                          retry_callback);
+
+  DCHECK(syncer::Intersection(active_types, types_to_purge).Empty());
+  DCHECK(syncer::Intersection(active_types, fatal_types).Empty());
+  DCHECK(syncer::Intersection(active_types, unapply_types).Empty());
+  DCHECK(syncer::Intersection(active_types, inactive_types).Empty());
+  return syncer::Difference(active_types, types_to_download);
 }
 
 void SyncBackendHostImpl::EnableEncryptEverything() {

chrome/browser/sync/glue/sync_backend_host_impl.h

@@ -100,7 +100,7 @@ class SyncBackendHostImpl
   void StopSyncingForShutdown() override;
   scoped_ptr<base::Thread> Shutdown(syncer::ShutdownReason reason) override;
   void UnregisterInvalidationIds() override;
-  void ConfigureDataTypes(
+  syncer::ModelTypeSet ConfigureDataTypes(
       syncer::ConfigureReason reason,
       const DataTypeConfigStateMap& config_state_map,
       const base::Callback<void(syncer::ModelTypeSet, syncer::ModelTypeSet)>&

chrome/browser/sync/glue/sync_backend_host_mock.cc

@@ -55,12 +55,14 @@ scoped_ptr<base::Thread> SyncBackendHostMock::Shutdown(
 
 void SyncBackendHostMock::UnregisterInvalidationIds() {}
 
-void SyncBackendHostMock::ConfigureDataTypes(
+syncer::ModelTypeSet SyncBackendHostMock::ConfigureDataTypes(
     syncer::ConfigureReason reason,
     const DataTypeConfigStateMap& config_state_map,
-    const base::Callback<void(syncer::ModelTypeSet,
-                              syncer::ModelTypeSet)>& ready_task,
-    const base::Callback<void()>& retry_callback) {}
+    const base::Callback<void(syncer::ModelTypeSet, syncer::ModelTypeSet)>&
+        ready_task,
+    const base::Callback<void()>& retry_callback) {
+  return syncer::ModelTypeSet();
+}
 
 void SyncBackendHostMock::EnableEncryptEverything() {}
 

chrome/browser/sync/glue/sync_backend_host_mock.h

@@ -53,7 +53,7 @@ class SyncBackendHostMock : public SyncBackendHost {
 
   void UnregisterInvalidationIds() override;
 
-  void ConfigureDataTypes(
+  syncer::ModelTypeSet ConfigureDataTypes(
       syncer::ConfigureReason reason,
       const DataTypeConfigStateMap& config_state_map,
       const base::Callback<void(syncer::ModelTypeSet, syncer::ModelTypeSet)>&

components/sync_driver/backend_data_type_configurer.h

@@ -42,17 +42,19 @@ class BackendDataTypeConfigurer {
   // is called when configuration is done with the set of data types
   // that succeeded/failed configuration (i.e., configuration succeeded iff
   // the failed set is empty).
+  // Returns: the set of types that are already configured and are ready to
+  // start.
   //
   // TODO(akalin): Use a Delegate class with
   // OnConfigureSuccess/OnConfigureFailure/OnConfigureRetry instead of
   // a pair of callbacks.  The awkward part is handling when
   // SyncBackendHost calls ConfigureDataTypes on itself to configure
   // Nigori.
-  virtual void ConfigureDataTypes(
+  virtual syncer::ModelTypeSet ConfigureDataTypes(
       syncer::ConfigureReason reason,
       const DataTypeConfigStateMap& config_state_map,
-      const base::Callback<void(syncer::ModelTypeSet,
-                                syncer::ModelTypeSet)>& ready_task,
+      const base::Callback<void(syncer::ModelTypeSet, syncer::ModelTypeSet)>&
+          ready_task,
       const base::Callback<void()>& retry_callback) = 0;
 
   // Return model types in |state_map| that match |state|.

components/sync_driver/data_type_manager_impl_unittest.cc

@@ -82,7 +82,7 @@ class FakeBackendDataTypeConfigurer : public BackendDataTypeConfigurer {
   FakeBackendDataTypeConfigurer() {}
   ~FakeBackendDataTypeConfigurer() override {}
 
-  void ConfigureDataTypes(
+  syncer::ModelTypeSet ConfigureDataTypes(
       syncer::ConfigureReason reason,
       const DataTypeConfigStateMap& config_state_map,
       const base::Callback<void(ModelTypeSet, ModelTypeSet)>& ready_task,
@@ -98,6 +98,7 @@ class FakeBackendDataTypeConfigurer : public BackendDataTypeConfigurer {
           << ModelTypeSetToString(
               GetDataTypesInState(CONFIGURE_ACTIVE, config_state_map));
     }
+    return syncer::ModelTypeSet();
   }
 
   void ActivateDataType(syncer::ModelType type,