Revert of [Sync] Refactor AttachmentStore classes. Introduce concept of referrer.

sync/internal_api/attachments/attachment_store_handle.cc

Index: sync/internal_api/attachments/attachment_store_handle.cc
diff --git a/sync/internal_api/attachments/attachment_store_handle.cc b/sync/internal_api/attachments/attachment_store_handle.cc
new file mode 100644
index 0000000000000000000000000000000000000000..5e3591b7e4dfaf7c7a730008b827e0f4b13cd876
--- /dev/null
+++ b/sync/internal_api/attachments/attachment_store_handle.cc
@@ -0,0 +1,88 @@
+// Copyright 2014 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 "sync/internal_api/public/attachments/attachment_store_handle.h"
+
+#include "base/bind.h"
+#include "base/location.h"
+#include "base/sequenced_task_runner.h"
+#include "sync/api/attachments/attachment.h"
+
+namespace syncer {
+
+namespace {
+
+// NoOp is needed to bind base::Passed(backend) in AttachmentStoreHandle dtor.
+// It doesn't need to do anything.
+void NoOp(scoped_ptr<AttachmentStoreBackend> backend) {
+}
+
+}  // namespace
+
+AttachmentStoreHandle::AttachmentStoreHandle(
+    scoped_ptr<AttachmentStoreBackend> backend,
+    const scoped_refptr<base::SequencedTaskRunner>& backend_task_runner)
+    : backend_(backend.Pass()), backend_task_runner_(backend_task_runner) {
+  DCHECK(backend_);
+  DCHECK(backend_task_runner_.get());
+}
+
+AttachmentStoreHandle::~AttachmentStoreHandle() {
+  DCHECK(backend_);
+  // To delete backend post task that doesn't do anything, but binds backend
+  // through base::Passed. This way backend will be deleted regardless whether
+  // task runs or not.
+  backend_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&NoOp, base::Passed(&backend_)));
+}
+
+void AttachmentStoreHandle::Init(const InitCallback& callback) {
+  DCHECK(CalledOnValidThread());
+  backend_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&AttachmentStoreBackend::Init,
+                            base::Unretained(backend_.get()), callback));
+}
+
+void AttachmentStoreHandle::Read(const AttachmentIdList& ids,
+                                 const ReadCallback& callback) {
+  DCHECK(CalledOnValidThread());
+  backend_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&AttachmentStoreBackend::Read,
+                            base::Unretained(backend_.get()), ids, callback));
+}
+
+void AttachmentStoreHandle::Write(const AttachmentList& attachments,
+                                  const WriteCallback& callback) {
+  DCHECK(CalledOnValidThread());
+  backend_task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&AttachmentStoreBackend::Write,
+                 base::Unretained(backend_.get()), attachments, callback));
+}
+
+void AttachmentStoreHandle::Drop(const AttachmentIdList& ids,
+                                 const DropCallback& callback) {
+  DCHECK(CalledOnValidThread());
+  backend_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&AttachmentStoreBackend::Drop,
+                            base::Unretained(backend_.get()), ids, callback));
+}
+
+void AttachmentStoreHandle::ReadMetadata(const AttachmentIdList& ids,
+                                         const ReadMetadataCallback& callback) {
+  DCHECK(CalledOnValidThread());
+  backend_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&AttachmentStoreBackend::ReadMetadata,
+                            base::Unretained(backend_.get()), ids, callback));
+}
+
+void AttachmentStoreHandle::ReadAllMetadata(
+    const ReadMetadataCallback& callback) {
+  DCHECK(CalledOnValidThread());
+  backend_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&AttachmentStoreBackend::ReadAllMetadata,
+                            base::Unretained(backend_.get()), callback));
+}
+
+}  // namespace syncer