[SyncFS] Drop TaskRunner in MetadataDatabase

Drop TaskRunner in MetadataDatabase, that is no longer needed.

BUG=412367

Review URL: https://codereview.chromium.org/556803002

Cr-Commit-Position: refs/heads/master@{#293937}

chrome/browser/sync_file_system/drive_backend/metadata_database.h

@@ -133,7 +133,6 @@ class MetadataDatabase {
   // of leveldb::Env::Default().  Use leveldb::MemEnv in test code for faster
   // testing.
   static void Create(
-      const scoped_refptr<base::SequencedTaskRunner>& worker_task_runner,
       const base::FilePath& database_path,
       leveldb::Env* env_override,
       const CreateCallback& callback);
@@ -356,7 +355,6 @@ class MetadataDatabase {
   struct CreateParam;
 
   MetadataDatabase(
-      const scoped_refptr<base::SequencedTaskRunner>& worker_task_runner,
       const base::FilePath& database_path,
       bool enable_on_disk_index,
       leveldb::Env* env_override);
@@ -411,10 +409,8 @@ class MetadataDatabase {
                                   const std::string& title,
                                   const std::string& file_id);
 
-  void DetachFromSequence();
   bool CanClearDirty(const FileTracker& tracker);
 
-  scoped_refptr<base::SequencedTaskRunner> worker_task_runner_;
   base::FilePath database_path_;
   leveldb::Env* env_override_;
   scoped_ptr<LevelDBWrapper> db_;
@@ -427,8 +423,6 @@ class MetadataDatabase {
 
   base::WeakPtrFactory<MetadataDatabase> weak_ptr_factory_;
 
-  base::SequenceChecker worker_sequence_checker_;
-
   DISALLOW_COPY_AND_ASSIGN(MetadataDatabase);
 };
 

chrome/browser/sync_file_system/drive_backend/metadata_database_unittest.cc

@@ -202,8 +202,7 @@ class MetadataDatabaseTest : public testing::Test {
 
   SyncStatusCode InitializeMetadataDatabase() {
     SyncStatusCode status = SYNC_STATUS_UNKNOWN;
-    MetadataDatabase::Create(base::ThreadTaskRunnerHandle::Get(),
-                             database_dir_.path(),
+    MetadataDatabase::Create(database_dir_.path(),
                              in_memory_env_.get(),
                              CreateResultReceiver(&status,
                                                   &metadata_database_));

chrome/browser/sync_file_system/drive_backend/sync_engine_initializer.cc

@@ -86,7 +86,6 @@ void SyncEngineInitializer::RunPreflight(scoped_ptr<SyncTaskToken> token) {
   }
 
   MetadataDatabase::Create(
-      sync_context_->GetWorkerTaskRunner(),
       database_path_,
       env_override_,
       base::Bind(&SyncEngineInitializer::DidCreateMetadataDatabase,

chrome/browser/sync_file_system/drive_backend/sync_engine_initializer_unittest.cc

@@ -109,7 +109,6 @@ class SyncEngineInitializerTest : public testing::Test {
     SyncStatusCode status = SYNC_STATUS_UNKNOWN;
     scoped_ptr<MetadataDatabase> database;
     MetadataDatabase::Create(
-        base::ThreadTaskRunnerHandle::Get(),
         database_path(),
         in_memory_env_.get(),
         CreateResultReceiver(&status, &database));