Revert of [Sync] Make directory types registration explicit in ModelTypeRegistry

components/sync/engine_impl/model_type_registry.cc

Index: components/sync/engine_impl/model_type_registry.cc
diff --git a/components/sync/engine_impl/model_type_registry.cc b/components/sync/engine_impl/model_type_registry.cc
index 33af95140d931473ee9971212d722a80fa7c615e..72450f479134cda02b5a7c6de4a31b2a2d38057a 100644
--- a/components/sync/engine_impl/model_type_registry.cc
+++ b/components/sync/engine_impl/model_type_registry.cc
@@ -71,7 +71,72 @@
 
 ModelTypeRegistry::~ModelTypeRegistry() {}
 
-void ModelTypeRegistry::ConnectNonBlockingType(
+void ModelTypeRegistry::SetEnabledDirectoryTypes(
+    const ModelSafeRoutingInfo& routing_info) {
+  // Remove all existing directory processors and delete them.  The
+  // DebugInfoEmitters are not deleted here, since we want to preserve their
+  // counters.
+  for (ModelTypeSet::Iterator it = enabled_directory_types_.First(); it.Good();
+       it.Inc()) {
+    size_t result1 = update_handler_map_.erase(it.Get());
+    size_t result2 = commit_contributor_map_.erase(it.Get());
+    DCHECK_EQ(1U, result1);
+    DCHECK_EQ(1U, result2);
+  }
+
+  // Clear the old instances of directory update handlers and commit
+  // contributors, deleting their contents in the processs.
+  directory_update_handlers_.clear();
+  directory_commit_contributors_.clear();
+
+  enabled_directory_types_.Clear();
+
+  // Create new ones and add them to the appropriate containers.
+  for (const auto& routing_kv : routing_info) {
+    ModelType type = routing_kv.first;
+    ModelSafeGroup group = routing_kv.second;
+    if (group == GROUP_NON_BLOCKING)
+      continue;
+
+    std::map<ModelSafeGroup, scoped_refptr<ModelSafeWorker>>::iterator
+        worker_it = workers_map_.find(group);
+    DCHECK(worker_it != workers_map_.end());
+    scoped_refptr<ModelSafeWorker> worker = worker_it->second;
+
+    DataTypeDebugInfoEmitter* emitter = GetEmitter(type);
+    if (emitter == nullptr) {
+      auto new_emitter = base::MakeUnique<DirectoryTypeDebugInfoEmitter>(
+          directory(), type, &type_debug_info_observers_);
+      emitter = new_emitter.get();
+      data_type_debug_info_emitter_map_.insert(
+          std::make_pair(type, std::move(new_emitter)));
+    }
+
+    auto updater = base::MakeUnique<DirectoryUpdateHandler>(directory(), type,
+                                                            worker, emitter);
+    bool updater_inserted =
+        update_handler_map_.insert(std::make_pair(type, updater.get())).second;
+    DCHECK(updater_inserted)
+        << "Attempt to override existing type handler in map";
+    directory_update_handlers_.push_back(std::move(updater));
+
+    auto committer = base::MakeUnique<DirectoryCommitContributor>(
+        directory(), type, emitter);
+    bool committer_inserted =
+        commit_contributor_map_.insert(std::make_pair(type, committer.get()))
+            .second;
+    DCHECK(committer_inserted)
+        << "Attempt to override existing type handler in map";
+    directory_commit_contributors_.push_back(std::move(committer));
+
+    enabled_directory_types_.Put(type);
+  }
+
+  DCHECK(Intersection(GetEnabledDirectoryTypes(), GetEnabledNonBlockingTypes())
+             .Empty());
+}
+
+void ModelTypeRegistry::ConnectType(
     ModelType type,
     std::unique_ptr<ActivationContext> activation_context) {
   DCHECK(update_handler_map_.find(type) == update_handler_map_.end());
@@ -139,7 +204,7 @@
              .Empty());
 }
 
-void ModelTypeRegistry::DisconnectNonBlockingType(ModelType type) {
+void ModelTypeRegistry::DisconnectType(ModelType type) {
   DVLOG(1) << "Disabling an off-thread sync type: " << ModelTypeToString(type);
   DCHECK(update_handler_map_.find(type) != update_handler_map_.end());
   DCHECK(commit_contributor_map_.find(type) != commit_contributor_map_.end());
@@ -158,58 +223,6 @@
       ++iter;
     }
   }
-}
-
-void ModelTypeRegistry::RegisterDirectoryType(ModelType type,
-                                              ModelSafeGroup group) {
-  DCHECK(update_handler_map_.find(type) == update_handler_map_.end());
-  DCHECK(commit_contributor_map_.find(type) == commit_contributor_map_.end());
-  DCHECK(directory_update_handlers_.find(type) ==
-         directory_update_handlers_.end());
-  DCHECK(directory_commit_contributors_.find(type) ==
-         directory_commit_contributors_.end());
-  DCHECK(data_type_debug_info_emitter_map_.find(type) ==
-         data_type_debug_info_emitter_map_.end());
-  DCHECK_NE(GROUP_NON_BLOCKING, group);
-  DCHECK(workers_map_.find(group) != workers_map_.end());
-
-  auto worker = workers_map_[group];
-  DCHECK(GetEmitter(type) == nullptr);
-  auto owned_emitter = base::MakeUnique<DirectoryTypeDebugInfoEmitter>(
-      directory(), type, &type_debug_info_observers_);
-  DataTypeDebugInfoEmitter* emitter_ptr = owned_emitter.get();
-  data_type_debug_info_emitter_map_[type] = std::move(owned_emitter);
-
-  auto updater = base::MakeUnique<DirectoryUpdateHandler>(directory(), type,
-                                                          worker, emitter_ptr);
-  auto committer = base::MakeUnique<DirectoryCommitContributor>(
-      directory(), type, emitter_ptr);
-
-  update_handler_map_[type] = updater.get();
-  commit_contributor_map_[type] = committer.get();
-
-  directory_update_handlers_[type] = std::move(updater);
-  directory_commit_contributors_[type] = std::move(committer);
-
-  DCHECK(Intersection(GetEnabledDirectoryTypes(), GetEnabledNonBlockingTypes())
-             .Empty());
-}
-
-void ModelTypeRegistry::UnregisterDirectoryType(ModelType type) {
-  DCHECK(update_handler_map_.find(type) != update_handler_map_.end());
-  DCHECK(commit_contributor_map_.find(type) != commit_contributor_map_.end());
-  DCHECK(directory_update_handlers_.find(type) !=
-         directory_update_handlers_.end());
-  DCHECK(directory_commit_contributors_.find(type) !=
-         directory_commit_contributors_.end());
-  DCHECK(data_type_debug_info_emitter_map_.find(type) !=
-         data_type_debug_info_emitter_map_.end());
-
-  update_handler_map_.erase(type);
-  commit_contributor_map_.erase(type);
-  directory_update_handlers_.erase(type);
-  directory_commit_contributors_.erase(type);
-  data_type_debug_info_emitter_map_.erase(type);
 }
 
 ModelTypeSet ModelTypeRegistry::GetEnabledTypes() const {
@@ -338,10 +351,7 @@
 }
 
 ModelTypeSet ModelTypeRegistry::GetEnabledDirectoryTypes() const {
-  ModelTypeSet enabled_directory_types;
-  for (const auto& kv : directory_update_handlers_)
-    enabled_directory_types.Put(kv.first);
-  return enabled_directory_types;
+  return enabled_directory_types_;
 }
 
 ModelTypeSet ModelTypeRegistry::GetEnabledNonBlockingTypes() const {