Move Indexed DB from dedicated thread to task scheduler

content/browser/indexed_db/database_impl.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/indexed_db/database_impl.h"
 
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/numerics/safe_math.h"
+#include "base/sequence_checker.h"
 #include "base/sequenced_task_runner.h"
-#include "base/threading/thread_checker.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "content/browser/bad_message.h"
 #include "content/browser/child_process_security_policy_impl.h"
 #include "content/browser/indexed_db/indexed_db_connection.h"
 #include "content/browser/indexed_db/indexed_db_context_impl.h"
 #include "content/browser/indexed_db/indexed_db_dispatcher_host.h"
 #include "content/browser/indexed_db/indexed_db_transaction.h"
 #include "content/browser/indexed_db/indexed_db_value.h"
 #include "storage/browser/blob/blob_storage_context.h"
 #include "storage/browser/quota/quota_manager_proxy.h"
 #include "third_party/WebKit/public/platform/modules/indexeddb/WebIDBDatabaseException.h"
 
 using std::swap;
 
 namespace content {
 class IndexedDBDatabaseError;
 
 namespace {
 const char kInvalidBlobUuid[] = "Blob does not exist";
 const char kInvalidBlobFilePath[] = "Blob file path is invalid";
 }  // namespace
 
-// Expect to be created on IO thread, and called/destroyed on IDB thread.
-class DatabaseImpl::IDBThreadHelper {
+// Expect to be created on IO thread, and called/destroyed on IDB sequence.
+class DatabaseImpl::IDBSequenceHelper {
  public:
-  IDBThreadHelper(std::unique_ptr<IndexedDBConnection> connection,
-                  const url::Origin& origin,
-                  scoped_refptr<IndexedDBContextImpl> indexed_db_context);
-  ~IDBThreadHelper();
+  IDBSequenceHelper(std::unique_ptr<IndexedDBConnection> connection,
+                    const url::Origin& origin,
+                    scoped_refptr<IndexedDBContextImpl> indexed_db_context);
+  ~IDBSequenceHelper();
 
   void ConnectionOpened();
 
   void CreateObjectStore(int64_t transaction_id,
                          int64_t object_store_id,
                          const base::string16& name,
                          const IndexedDBKeyPath& key_path,
                          bool auto_increment);
   void DeleteObjectStore(int64_t transaction_id, int64_t object_store_id);
   void RenameObjectStore(int64_t transaction_id,
@@ skipping 82 matching lines @@
   void OnGotUsageAndQuotaForCommit(int64_t transaction_id,
                                    storage::QuotaStatusCode status,
                                    int64_t usage,
                                    int64_t quota);
   void AckReceivedBlobs(const std::vector<std::string>& uuids);
 
  private:
   scoped_refptr<IndexedDBContextImpl> indexed_db_context_;
   std::unique_ptr<IndexedDBConnection> connection_;
   const url::Origin origin_;
-  base::ThreadChecker idb_thread_checker_;
-  base::WeakPtrFactory<IDBThreadHelper> weak_factory_;
+  SEQUENCE_CHECKER(sequence_checker_);
+  base::WeakPtrFactory<IDBSequenceHelper> weak_factory_;
 };
 
 DatabaseImpl::DatabaseImpl(std::unique_ptr<IndexedDBConnection> connection,
                            const url::Origin& origin,
                            IndexedDBDispatcherHost* dispatcher_host,
                            scoped_refptr<base::SequencedTaskRunner> idb_runner)
     : dispatcher_host_(dispatcher_host),
       origin_(origin),
       idb_runner_(std::move(idb_runner)) {
   DCHECK(connection);
-  helper_ = new IDBThreadHelper(std::move(connection), origin,
-                                dispatcher_host->context());
+  helper_ = new IDBSequenceHelper(std::move(connection), origin,
+                                  dispatcher_host->context());
   idb_runner_->PostTask(FROM_HERE,
-                        base::Bind(&IDBThreadHelper::ConnectionOpened,
+                        base::Bind(&IDBSequenceHelper::ConnectionOpened,
                                    base::Unretained(helper_)));
 }
 
 DatabaseImpl::~DatabaseImpl() {
   idb_runner_->DeleteSoon(FROM_HERE, helper_);
 }
 
 void DatabaseImpl::CreateObjectStore(int64_t transaction_id,
                                      int64_t object_store_id,
                                      const base::string16& name,
                                      const IndexedDBKeyPath& key_path,
                                      bool auto_increment) {
   idb_runner_->PostTask(
-      FROM_HERE, base::Bind(&IDBThreadHelper::CreateObjectStore,
+      FROM_HERE, base::Bind(&IDBSequenceHelper::CreateObjectStore,
                             base::Unretained(helper_), transaction_id,
                             object_store_id, name, key_path, auto_increment));
 }
 
 void DatabaseImpl::DeleteObjectStore(int64_t transaction_id,
                                      int64_t object_store_id) {
   idb_runner_->PostTask(
       FROM_HERE,
-      base::Bind(&IDBThreadHelper::DeleteObjectStore, base::Unretained(helper_),
-                 transaction_id, object_store_id));
+      base::Bind(&IDBSequenceHelper::DeleteObjectStore,
+                 base::Unretained(helper_), transaction_id, object_store_id));
 }
 
 void DatabaseImpl::RenameObjectStore(int64_t transaction_id,
                                      int64_t object_store_id,
                                      const base::string16& new_name) {
-  idb_runner_->PostTask(
-      FROM_HERE,
-      base::Bind(&IDBThreadHelper::RenameObjectStore, base::Unretained(helper_),
-                 transaction_id, object_store_id, new_name));
+  idb_runner_->PostTask(FROM_HERE,
+                        base::Bind(&IDBSequenceHelper::RenameObjectStore,
+                                   base::Unretained(helper_), transaction_id,
+                                   object_store_id, new_name));
 }
 
 void DatabaseImpl::CreateTransaction(
     int64_t transaction_id,
     const std::vector<int64_t>& object_store_ids,
     blink::WebIDBTransactionMode mode) {
-  idb_runner_->PostTask(
-      FROM_HERE,
-      base::Bind(&IDBThreadHelper::CreateTransaction, base::Unretained(helper_),
-                 transaction_id, object_store_ids, mode));
+  idb_runner_->PostTask(FROM_HERE,
+                        base::Bind(&IDBSequenceHelper::CreateTransaction,
+                                   base::Unretained(helper_), transaction_id,
+                                   object_store_ids, mode));
 }
 
 void DatabaseImpl::Close() {
-  idb_runner_->PostTask(FROM_HERE, base::Bind(&IDBThreadHelper::Close,
+  idb_runner_->PostTask(FROM_HERE, base::Bind(&IDBSequenceHelper::Close,
                                               base::Unretained(helper_)));
 }
 
 void DatabaseImpl::VersionChangeIgnored() {
   idb_runner_->PostTask(FROM_HERE,
-                        base::Bind(&IDBThreadHelper::VersionChangeIgnored,
+                        base::Bind(&IDBSequenceHelper::VersionChangeIgnored,
                                    base::Unretained(helper_)));
 }
 
 void DatabaseImpl::AddObserver(int64_t transaction_id,
                                int32_t observer_id,
                                bool include_transaction,
                                bool no_records,
                                bool values,
                                uint16_t operation_types) {
   idb_runner_->PostTask(
       FROM_HERE,
-      base::Bind(&IDBThreadHelper::AddObserver, base::Unretained(helper_),
+      base::Bind(&IDBSequenceHelper::AddObserver, base::Unretained(helper_),
                  transaction_id, observer_id, include_transaction, no_records,
                  values, operation_types));
 }
 
 void DatabaseImpl::RemoveObservers(const std::vector<int32_t>& observers) {
   idb_runner_->PostTask(FROM_HERE,
-                        base::Bind(&IDBThreadHelper::RemoveObservers,
+                        base::Bind(&IDBSequenceHelper::RemoveObservers,
                                    base::Unretained(helper_), observers));
 }
 
 void DatabaseImpl::Get(
     int64_t transaction_id,
     int64_t object_store_id,
     int64_t index_id,
     const IndexedDBKeyRange& key_range,
     bool key_only,
     ::indexed_db::mojom::CallbacksAssociatedPtrInfo callbacks_info) {
   scoped_refptr<IndexedDBCallbacks> callbacks(
       new IndexedDBCallbacks(dispatcher_host_->AsWeakPtr(), origin_,
                              std::move(callbacks_info), idb_runner_));
   idb_runner_->PostTask(
-      FROM_HERE, base::Bind(&IDBThreadHelper::Get, base::Unretained(helper_),
+      FROM_HERE, base::Bind(&IDBSequenceHelper::Get, base::Unretained(helper_),
                             transaction_id, object_store_id, index_id,
                             key_range, key_only, base::Passed(&callbacks)));
 }
 
 void DatabaseImpl::GetAll(
     int64_t transaction_id,
     int64_t object_store_id,
     int64_t index_id,
     const IndexedDBKeyRange& key_range,
     bool key_only,
     int64_t max_count,
     ::indexed_db::mojom::CallbacksAssociatedPtrInfo callbacks_info) {
   scoped_refptr<IndexedDBCallbacks> callbacks(
       new IndexedDBCallbacks(dispatcher_host_->AsWeakPtr(), origin_,
                              std::move(callbacks_info), idb_runner_));
   idb_runner_->PostTask(
       FROM_HERE,
-      base::Bind(&IDBThreadHelper::GetAll, base::Unretained(helper_),
+      base::Bind(&IDBSequenceHelper::GetAll, base::Unretained(helper_),
                  transaction_id, object_store_id, index_id, key_range, key_only,
                  max_count, base::Passed(&callbacks)));
 }
 
 void DatabaseImpl::Put(
     int64_t transaction_id,
     int64_t object_store_id,
     ::indexed_db::mojom::ValuePtr value,
     const IndexedDBKey& key,
     blink::WebIDBPutMode mode,
@@ skipping 19 matching lines @@
 
     // Due to known issue crbug.com/351753, blobs can die while being passed to
     // a different process. So this case must be handled gracefully.
     // TODO(dmurph): Revert back to using mojo::ReportBadMessage once fixed.
     UMA_HISTOGRAM_BOOLEAN("Storage.IndexedDB.PutValidBlob",
                           handle.get() != nullptr);
     if (!handle) {
       IndexedDBDatabaseError error(blink::kWebIDBDatabaseExceptionUnknownError,
                                    kInvalidBlobUuid);
       idb_runner_->PostTask(
-          FROM_HERE, base::Bind(&IDBThreadHelper::AbortWithError,
+          FROM_HERE, base::Bind(&IDBSequenceHelper::AbortWithError,
                                 base::Unretained(helper_), transaction_id,
                                 base::Passed(&callbacks), error));
       return;
     }
     uint64_t size = handle->size();
     UMA_HISTOGRAM_MEMORY_KB("Storage.IndexedDB.PutBlobSizeKB", size / 1024ull);
     total_blob_size += size;
     handles[i] = std::move(handle);
 
     if (info->file) {
@@ skipping 17 matching lines @@
                             blob_info.size());
   uint64_t blob_size = 0;
   total_blob_size.AssignIfValid(&blob_size);
   if (blob_size != 0) {
     // 1KB to 1GB.
     UMA_HISTOGRAM_COUNTS_1M("WebCore.IndexedDB.PutBlobsTotalSize",
                             blob_size / 1024);
   }
   idb_runner_->PostTask(
       FROM_HERE,
-      base::Bind(&IDBThreadHelper::Put, base::Unretained(helper_),
+      base::Bind(&IDBSequenceHelper::Put, base::Unretained(helper_),
                  transaction_id, object_store_id, base::Passed(&value),
                  base::Passed(&handles), base::Passed(&blob_info), key, mode,
                  index_keys, base::Passed(&callbacks)));
 }
 
 void DatabaseImpl::SetIndexKeys(
     int64_t transaction_id,
     int64_t object_store_id,
     const IndexedDBKey& primary_key,
     const std::vector<IndexedDBIndexKeys>& index_keys) {
   idb_runner_->PostTask(
       FROM_HERE,
-      base::Bind(&IDBThreadHelper::SetIndexKeys, base::Unretained(helper_),
+      base::Bind(&IDBSequenceHelper::SetIndexKeys, base::Unretained(helper_),
                  transaction_id, object_store_id, primary_key, index_keys));
 }
 
 void DatabaseImpl::SetIndexesReady(int64_t transaction_id,
                                    int64_t object_store_id,
                                    const std::vector<int64_t>& index_ids) {
   idb_runner_->PostTask(
       FROM_HERE,
-      base::Bind(&IDBThreadHelper::SetIndexesReady, base::Unretained(helper_),
+      base::Bind(&IDBSequenceHelper::SetIndexesReady, base::Unretained(helper_),
                  transaction_id, object_store_id, index_ids));
 }
 
 void DatabaseImpl::OpenCursor(
     int64_t transaction_id,
     int64_t object_store_id,
     int64_t index_id,
     const IndexedDBKeyRange& key_range,
     blink::WebIDBCursorDirection direction,
     bool key_only,
     blink::WebIDBTaskType task_type,
     ::indexed_db::mojom::CallbacksAssociatedPtrInfo callbacks_info) {
   scoped_refptr<IndexedDBCallbacks> callbacks(
       new IndexedDBCallbacks(dispatcher_host_->AsWeakPtr(), origin_,
                              std::move(callbacks_info), idb_runner_));
   idb_runner_->PostTask(
       FROM_HERE,
-      base::Bind(&IDBThreadHelper::OpenCursor, base::Unretained(helper_),
+      base::Bind(&IDBSequenceHelper::OpenCursor, base::Unretained(helper_),
                  transaction_id, object_store_id, index_id, key_range,
                  direction, key_only, task_type, base::Passed(&callbacks)));
 }
 
 void DatabaseImpl::Count(
     int64_t transaction_id,
     int64_t object_store_id,
     int64_t index_id,
     const IndexedDBKeyRange& key_range,
     ::indexed_db::mojom::CallbacksAssociatedPtrInfo callbacks_info) {
   scoped_refptr<IndexedDBCallbacks> callbacks(
       new IndexedDBCallbacks(dispatcher_host_->AsWeakPtr(), origin_,
                              std::move(callbacks_info), idb_runner_));
   idb_runner_->PostTask(
-      FROM_HERE, base::Bind(&IDBThreadHelper::Count, base::Unretained(helper_),
-                            transaction_id, object_store_id, index_id,
-                            key_range, base::Passed(&callbacks)));
+      FROM_HERE,
+      base::Bind(&IDBSequenceHelper::Count, base::Unretained(helper_),
+                 transaction_id, object_store_id, index_id, key_range,
+                 base::Passed(&callbacks)));
 }
 
 void DatabaseImpl::DeleteRange(
     int64_t transaction_id,
     int64_t object_store_id,
     const IndexedDBKeyRange& key_range,
     ::indexed_db::mojom::CallbacksAssociatedPtrInfo callbacks_info) {
   scoped_refptr<IndexedDBCallbacks> callbacks(
       new IndexedDBCallbacks(dispatcher_host_->AsWeakPtr(), origin_,
                              std::move(callbacks_info), idb_runner_));
   idb_runner_->PostTask(
       FROM_HERE,
-      base::Bind(&IDBThreadHelper::DeleteRange, base::Unretained(helper_),
+      base::Bind(&IDBSequenceHelper::DeleteRange, base::Unretained(helper_),
                  transaction_id, object_store_id, key_range,
                  base::Passed(&callbacks)));
 }
 
 void DatabaseImpl::Clear(
     int64_t transaction_id,
     int64_t object_store_id,
     ::indexed_db::mojom::CallbacksAssociatedPtrInfo callbacks_info) {
   scoped_refptr<IndexedDBCallbacks> callbacks(
       new IndexedDBCallbacks(dispatcher_host_->AsWeakPtr(), origin_,
                              std::move(callbacks_info), idb_runner_));
   idb_runner_->PostTask(
       FROM_HERE,
-      base::Bind(&IDBThreadHelper::Clear, base::Unretained(helper_),
+      base::Bind(&IDBSequenceHelper::Clear, base::Unretained(helper_),
                  transaction_id, object_store_id, base::Passed(&callbacks)));
 }
 
 void DatabaseImpl::CreateIndex(int64_t transaction_id,
                                int64_t object_store_id,
                                int64_t index_id,
                                const base::string16& name,
                                const IndexedDBKeyPath& key_path,
                                bool unique,
                                bool multi_entry) {
   idb_runner_->PostTask(
       FROM_HERE,
-      base::Bind(&IDBThreadHelper::CreateIndex, base::Unretained(helper_),
+      base::Bind(&IDBSequenceHelper::CreateIndex, base::Unretained(helper_),
                  transaction_id, object_store_id, index_id, name, key_path,
                  unique, multi_entry));
 }
 
 void DatabaseImpl::DeleteIndex(int64_t transaction_id,
                                int64_t object_store_id,
                                int64_t index_id) {
   idb_runner_->PostTask(
       FROM_HERE,
-      base::Bind(&IDBThreadHelper::DeleteIndex, base::Unretained(helper_),
+      base::Bind(&IDBSequenceHelper::DeleteIndex, base::Unretained(helper_),
                  transaction_id, object_store_id, index_id));
 }
 
 void DatabaseImpl::RenameIndex(int64_t transaction_id,
                                int64_t object_store_id,
                                int64_t index_id,
                                const base::string16& new_name) {
   idb_runner_->PostTask(
       FROM_HERE,
-      base::Bind(&IDBThreadHelper::RenameIndex, base::Unretained(helper_),
+      base::Bind(&IDBSequenceHelper::RenameIndex, base::Unretained(helper_),
                  transaction_id, object_store_id, index_id, new_name));
 }
 
 void DatabaseImpl::Abort(int64_t transaction_id) {
-  idb_runner_->PostTask(
-      FROM_HERE, base::Bind(&IDBThreadHelper::Abort, base::Unretained(helper_),
-                            transaction_id));
+  idb_runner_->PostTask(FROM_HERE,
+                        base::Bind(&IDBSequenceHelper::Abort,
+                                   base::Unretained(helper_), transaction_id));
 }
 
 void DatabaseImpl::Commit(int64_t transaction_id) {
-  idb_runner_->PostTask(
-      FROM_HERE, base::Bind(&IDBThreadHelper::Commit, base::Unretained(helper_),
-                            transaction_id));
+  idb_runner_->PostTask(FROM_HERE,
+                        base::Bind(&IDBSequenceHelper::Commit,
+                                   base::Unretained(helper_), transaction_id));
 }
 
 void DatabaseImpl::AckReceivedBlobs(const std::vector<std::string>& uuids) {
   for (const auto& uuid : uuids)
     dispatcher_host_->DropBlobData(uuid);
 }
 
-DatabaseImpl::IDBThreadHelper::IDBThreadHelper(
+DatabaseImpl::IDBSequenceHelper::IDBSequenceHelper(
     std::unique_ptr<IndexedDBConnection> connection,
     const url::Origin& origin,
     scoped_refptr<IndexedDBContextImpl> indexed_db_context)
     : indexed_db_context_(indexed_db_context),
       connection_(std::move(connection)),
       origin_(origin),
       weak_factory_(this) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
-  idb_thread_checker_.DetachFromThread();
+  DETACH_FROM_SEQUENCE(sequence_checker_);
 }
 
-DatabaseImpl::IDBThreadHelper::~IDBThreadHelper() {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+DatabaseImpl::IDBSequenceHelper::~IDBSequenceHelper() {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (connection_->IsConnected())
     connection_->Close();
   indexed_db_context_->ConnectionClosed(origin_, connection_.get());
 }
 
-void DatabaseImpl::IDBThreadHelper::ConnectionOpened() {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+void DatabaseImpl::IDBSequenceHelper::ConnectionOpened() {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   indexed_db_context_->ConnectionOpened(origin_, connection_.get());
 }
 
-void DatabaseImpl::IDBThreadHelper::CreateObjectStore(
+void DatabaseImpl::IDBSequenceHelper::CreateObjectStore(
     int64_t transaction_id,
     int64_t object_store_id,
     const base::string16& name,
     const IndexedDBKeyPath& key_path,
     bool auto_increment) {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!connection_->IsConnected())
     return;
 
   IndexedDBTransaction* transaction =
       connection_->GetTransaction(transaction_id);
   if (!transaction)
     return;
 
   connection_->database()->CreateObjectStore(transaction, object_store_id, name,
                                              key_path, auto_increment);
 }
 
-void DatabaseImpl::IDBThreadHelper::DeleteObjectStore(int64_t transaction_id,
-                                                      int64_t object_store_id) {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+void DatabaseImpl::IDBSequenceHelper::DeleteObjectStore(
+    int64_t transaction_id,
+    int64_t object_store_id) {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!connection_->IsConnected())
     return;
 
   IndexedDBTransaction* transaction =
       connection_->GetTransaction(transaction_id);
   if (!transaction)
     return;
 
   connection_->database()->DeleteObjectStore(transaction, object_store_id);
 }
 
-void DatabaseImpl::IDBThreadHelper::RenameObjectStore(
+void DatabaseImpl::IDBSequenceHelper::RenameObjectStore(
     int64_t transaction_id,
     int64_t object_store_id,
     const base::string16& new_name) {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!connection_->IsConnected())
     return;
 
   IndexedDBTransaction* transaction =
       connection_->GetTransaction(transaction_id);
   if (!transaction)
     return;
 
   connection_->database()->RenameObjectStore(transaction, object_store_id,
                                              new_name);
 }
 
-void DatabaseImpl::IDBThreadHelper::CreateTransaction(
+void DatabaseImpl::IDBSequenceHelper::CreateTransaction(
     int64_t transaction_id,
     const std::vector<int64_t>& object_store_ids,
     blink::WebIDBTransactionMode mode) {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!connection_->IsConnected())
     return;
 
   // Can't call BadMessage as we're no longer on the IO thread. So ignore.
   if (connection_->GetTransaction(transaction_id))
     return;
 
   connection_->database()->CreateTransaction(transaction_id, connection_.get(),
                                              object_store_ids, mode);
 }
 
-void DatabaseImpl::IDBThreadHelper::Close() {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+void DatabaseImpl::IDBSequenceHelper::Close() {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!connection_->IsConnected())
     return;
 
   connection_->Close();
 }
 
-void DatabaseImpl::IDBThreadHelper::VersionChangeIgnored() {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+void DatabaseImpl::IDBSequenceHelper::VersionChangeIgnored() {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!connection_->IsConnected())
     return;
 
   connection_->VersionChangeIgnored();
 }
 
-void DatabaseImpl::IDBThreadHelper::AddObserver(int64_t transaction_id,
-                                                int32_t observer_id,
-                                                bool include_transaction,
-                                                bool no_records,
-                                                bool values,
-                                                uint16_t operation_types) {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+void DatabaseImpl::IDBSequenceHelper::AddObserver(int64_t transaction_id,
+                                                  int32_t observer_id,
+                                                  bool include_transaction,
+                                                  bool no_records,
+                                                  bool values,
+                                                  uint16_t operation_types) {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!connection_->IsConnected())
     return;
 
   IndexedDBTransaction* transaction =
       connection_->GetTransaction(transaction_id);
   if (!transaction)
     return;
 
   IndexedDBObserver::Options options(include_transaction, no_records, values,
                                      operation_types);
   connection_->database()->AddPendingObserver(transaction, observer_id,
                                               options);
 }
 
-void DatabaseImpl::IDBThreadHelper::RemoveObservers(
+void DatabaseImpl::IDBSequenceHelper::RemoveObservers(
     const std::vector<int32_t>& observers) {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!connection_->IsConnected())
     return;
 
   connection_->RemoveObservers(observers);
 }
 
-void DatabaseImpl::IDBThreadHelper::Get(
+void DatabaseImpl::IDBSequenceHelper::Get(
     int64_t transaction_id,
     int64_t object_store_id,
     int64_t index_id,
     const IndexedDBKeyRange& key_range,
     bool key_only,
     scoped_refptr<IndexedDBCallbacks> callbacks) {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!connection_->IsConnected())
     return;
 
   IndexedDBTransaction* transaction =
       connection_->GetTransaction(transaction_id);
   if (!transaction)
     return;
 
   connection_->database()->Get(transaction, object_store_id, index_id,
                                base::MakeUnique<IndexedDBKeyRange>(key_range),
                                key_only, callbacks);
 }
 
-void DatabaseImpl::IDBThreadHelper::GetAll(
+void DatabaseImpl::IDBSequenceHelper::GetAll(
     int64_t transaction_id,
     int64_t object_store_id,
     int64_t index_id,
     const IndexedDBKeyRange& key_range,
     bool key_only,
     int64_t max_count,
     scoped_refptr<IndexedDBCallbacks> callbacks) {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!connection_->IsConnected())
     return;
 
   IndexedDBTransaction* transaction =
       connection_->GetTransaction(transaction_id);
   if (!transaction)
     return;
 
   connection_->database()->GetAll(
       transaction, object_store_id, index_id,
       base::MakeUnique<IndexedDBKeyRange>(key_range), key_only, max_count,
       std::move(callbacks));
 }
 
-void DatabaseImpl::IDBThreadHelper::Put(
+void DatabaseImpl::IDBSequenceHelper::Put(
     int64_t transaction_id,
     int64_t object_store_id,
     ::indexed_db::mojom::ValuePtr mojo_value,
     std::vector<std::unique_ptr<storage::BlobDataHandle>> handles,
     std::vector<IndexedDBBlobInfo> blob_info,
     const IndexedDBKey& key,
     blink::WebIDBPutMode mode,
     const std::vector<IndexedDBIndexKeys>& index_keys,
     scoped_refptr<IndexedDBCallbacks> callbacks) {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!connection_->IsConnected())
     return;
 
   IndexedDBTransaction* transaction =
       connection_->GetTransaction(transaction_id);
   if (!transaction)
     return;
 
   // Value size recorded in IDBObjectStore before we can auto-wrap in a blob.
   // 1KB to 10MB.
   UMA_HISTOGRAM_COUNTS_10000("WebCore.IndexedDB.PutKeySize",
                              key.size_estimate() / 1024);
 
   uint64_t commit_size = mojo_value->bits.size() + key.size_estimate();
   IndexedDBValue value;
   swap(value.bits, mojo_value->bits);
   swap(value.blob_info, blob_info);
   connection_->database()->Put(transaction, object_store_id, &value, &handles,
                                base::MakeUnique<IndexedDBKey>(key), mode,
                                std::move(callbacks), index_keys);
 
   // Size can't be big enough to overflow because it represents the
   // actual bytes passed through IPC.
   transaction->set_size(transaction->size() + commit_size);
 }
 
-void DatabaseImpl::IDBThreadHelper::SetIndexKeys(
+void DatabaseImpl::IDBSequenceHelper::SetIndexKeys(
     int64_t transaction_id,
     int64_t object_store_id,
     const IndexedDBKey& primary_key,
     const std::vector<IndexedDBIndexKeys>& index_keys) {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!connection_->IsConnected())
     return;
 
   IndexedDBTransaction* transaction =
       connection_->GetTransaction(transaction_id);
   if (!transaction)
     return;
 
   connection_->database()->SetIndexKeys(
       transaction, object_store_id, base::MakeUnique<IndexedDBKey>(primary_key),
       index_keys);
 }
 
-void DatabaseImpl::IDBThreadHelper::SetIndexesReady(
+void DatabaseImpl::IDBSequenceHelper::SetIndexesReady(
     int64_t transaction_id,
     int64_t object_store_id,
     const std::vector<int64_t>& index_ids) {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!connection_->IsConnected())
     return;
 
   IndexedDBTransaction* transaction =
       connection_->GetTransaction(transaction_id);
   if (!transaction)
     return;
 
   connection_->database()->SetIndexesReady(transaction, object_store_id,
                                            index_ids);
 }
 
-void DatabaseImpl::IDBThreadHelper::OpenCursor(
+void DatabaseImpl::IDBSequenceHelper::OpenCursor(
     int64_t transaction_id,
     int64_t object_store_id,
     int64_t index_id,
     const IndexedDBKeyRange& key_range,
     blink::WebIDBCursorDirection direction,
     bool key_only,
     blink::WebIDBTaskType task_type,
     scoped_refptr<IndexedDBCallbacks> callbacks) {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!connection_->IsConnected())
     return;
 
   IndexedDBTransaction* transaction =
       connection_->GetTransaction(transaction_id);
   if (!transaction)
     return;
 
   connection_->database()->OpenCursor(
       transaction, object_store_id, index_id,
       base::MakeUnique<IndexedDBKeyRange>(key_range), direction, key_only,
       task_type, std::move(callbacks));
 }
 
-void DatabaseImpl::IDBThreadHelper::Count(
+void DatabaseImpl::IDBSequenceHelper::Count(
     int64_t transaction_id,
     int64_t object_store_id,
     int64_t index_id,
     const IndexedDBKeyRange& key_range,
     scoped_refptr<IndexedDBCallbacks> callbacks) {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!connection_->IsConnected())
     return;
 
   IndexedDBTransaction* transaction =
       connection_->GetTransaction(transaction_id);
   if (!transaction)
     return;
 
   connection_->database()->Count(transaction, object_store_id, index_id,
                                  base::MakeUnique<IndexedDBKeyRange>(key_range),
                                  std::move(callbacks));
 }
 
-void DatabaseImpl::IDBThreadHelper::DeleteRange(
+void DatabaseImpl::IDBSequenceHelper::DeleteRange(
     int64_t transaction_id,
     int64_t object_store_id,
     const IndexedDBKeyRange& key_range,
     scoped_refptr<IndexedDBCallbacks> callbacks) {
   if (!connection_->IsConnected())
     return;
 
   IndexedDBTransaction* transaction =
       connection_->GetTransaction(transaction_id);
   if (!transaction)
     return;
 
   connection_->database()->DeleteRange(
       transaction, object_store_id,
       base::MakeUnique<IndexedDBKeyRange>(key_range), std::move(callbacks));
 }
 
-void DatabaseImpl::IDBThreadHelper::Clear(
+void DatabaseImpl::IDBSequenceHelper::Clear(
     int64_t transaction_id,
     int64_t object_store_id,
     scoped_refptr<IndexedDBCallbacks> callbacks) {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!connection_->IsConnected())
     return;
 
   IndexedDBTransaction* transaction =
       connection_->GetTransaction(transaction_id);
   if (!transaction)
     return;
 
   connection_->database()->Clear(transaction, object_store_id, callbacks);
 }
 
-void DatabaseImpl::IDBThreadHelper::CreateIndex(
+void DatabaseImpl::IDBSequenceHelper::CreateIndex(
     int64_t transaction_id,
     int64_t object_store_id,
     int64_t index_id,
     const base::string16& name,
     const IndexedDBKeyPath& key_path,
     bool unique,
     bool multi_entry) {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!connection_->IsConnected())
     return;
 
   IndexedDBTransaction* transaction =
       connection_->GetTransaction(transaction_id);
   if (!transaction)
     return;
 
   connection_->database()->CreateIndex(transaction, object_store_id, index_id,
                                        name, key_path, unique, multi_entry);
 }
 
-void DatabaseImpl::IDBThreadHelper::DeleteIndex(int64_t transaction_id,
-                                                int64_t object_store_id,
-                                                int64_t index_id) {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+void DatabaseImpl::IDBSequenceHelper::DeleteIndex(int64_t transaction_id,
+                                                  int64_t object_store_id,
+                                                  int64_t index_id) {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!connection_->IsConnected())
     return;
 
   IndexedDBTransaction* transaction =
       connection_->GetTransaction(transaction_id);
   if (!transaction)
     return;
 
   connection_->database()->DeleteIndex(transaction, object_store_id, index_id);
 }
 
-void DatabaseImpl::IDBThreadHelper::RenameIndex(
+void DatabaseImpl::IDBSequenceHelper::RenameIndex(
     int64_t transaction_id,
     int64_t object_store_id,
     int64_t index_id,
     const base::string16& new_name) {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!connection_->IsConnected())
     return;
 
   IndexedDBTransaction* transaction =
       connection_->GetTransaction(transaction_id);
   if (!transaction)
     return;
 
   connection_->database()->RenameIndex(transaction, object_store_id, index_id,
                                        new_name);
 }
 
-void DatabaseImpl::IDBThreadHelper::Abort(int64_t transaction_id) {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+void DatabaseImpl::IDBSequenceHelper::Abort(int64_t transaction_id) {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!connection_->IsConnected())
     return;
 
   IndexedDBTransaction* transaction =
       connection_->GetTransaction(transaction_id);
   if (!transaction)
     return;
 
   connection_->AbortTransaction(
       transaction,
       IndexedDBDatabaseError(blink::kWebIDBDatabaseExceptionAbortError,
                              "Transaction aborted by user."));
 }
 
-void DatabaseImpl::IDBThreadHelper::AbortWithError(
+void DatabaseImpl::IDBSequenceHelper::AbortWithError(
     int64_t transaction_id,
     scoped_refptr<IndexedDBCallbacks> callbacks,
     const IndexedDBDatabaseError& error) {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
 
   callbacks->OnError(error);
 
   if (!connection_->IsConnected())
     return;
 
   IndexedDBTransaction* transaction =
       connection_->GetTransaction(transaction_id);
   if (!transaction)
     return;
 
   connection_->AbortTransaction(transaction, error);
 }
 
-void DatabaseImpl::IDBThreadHelper::Commit(int64_t transaction_id) {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+void DatabaseImpl::IDBSequenceHelper::Commit(int64_t transaction_id) {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!connection_->IsConnected())
     return;
 
   IndexedDBTransaction* transaction =
       connection_->GetTransaction(transaction_id);
   if (!transaction)
     return;
 
   // Always allow empty or delete-only transactions.
   if (transaction->size() == 0) {
     connection_->database()->Commit(transaction);
     return;
   }
 
   indexed_db_context_->quota_manager_proxy()->GetUsageAndQuota(
       indexed_db_context_->TaskRunner(), origin_.GetURL(),
       storage::kStorageTypeTemporary,
-      base::Bind(&IDBThreadHelper::OnGotUsageAndQuotaForCommit,
+      base::Bind(&IDBSequenceHelper::OnGotUsageAndQuotaForCommit,
                  weak_factory_.GetWeakPtr(), transaction_id));
 }
 
-void DatabaseImpl::IDBThreadHelper::OnGotUsageAndQuotaForCommit(
+void DatabaseImpl::IDBSequenceHelper::OnGotUsageAndQuotaForCommit(
     int64_t transaction_id,
     storage::QuotaStatusCode status,
     int64_t usage,
     int64_t quota) {
-  DCHECK(idb_thread_checker_.CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   // May have disconnected while quota check was pending.
   if (!connection_->IsConnected())
     return;
 
   IndexedDBTransaction* transaction =
       connection_->GetTransaction(transaction_id);
   if (!transaction)
     return;
 
   if (status == storage::kQuotaStatusOk &&
       usage + transaction->size() <= quota) {
     connection_->database()->Commit(transaction);
   } else {
     connection_->AbortTransaction(
         transaction,
         IndexedDBDatabaseError(blink::kWebIDBDatabaseExceptionQuotaError));
   }
 }
 
 }  // namespace content