Deprecate NonThreadSafe in components/sync in favor of SequenceChecker.

components/sync/engine/attachments/attachment_store_frontend.cc

Index: components/sync/engine/attachments/attachment_store_frontend.cc
diff --git a/components/sync/engine/attachments/attachment_store_frontend.cc b/components/sync/engine/attachments/attachment_store_frontend.cc
index ffc50eb8efc3a9e1aa36d5527133472feab1d054..d67c2c14ed32f3b493b4d057a1aa6fbf1fd3ef45 100644
--- a/components/sync/engine/attachments/attachment_store_frontend.cc
+++ b/components/sync/engine/attachments/attachment_store_frontend.cc
@@ -31,6 +31,7 @@ AttachmentStoreFrontend::AttachmentStoreFrontend(
 }
 
 AttachmentStoreFrontend::~AttachmentStoreFrontend() {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   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
@@ -41,7 +42,7 @@ AttachmentStoreFrontend::~AttachmentStoreFrontend() {
 
 void AttachmentStoreFrontend::Init(
     const AttachmentStore::InitCallback& callback) {
-  DCHECK(CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   backend_task_runner_->PostTask(
       FROM_HERE, base::Bind(&AttachmentStoreBackend::Init,
                             base::Unretained(backend_.get()), callback));
@@ -51,7 +52,7 @@ void AttachmentStoreFrontend::Read(
     AttachmentStore::Component component,
     const AttachmentIdList& ids,
     const AttachmentStore::ReadCallback& callback) {
-  DCHECK(CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   backend_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&AttachmentStoreBackend::Read,
@@ -62,7 +63,7 @@ void AttachmentStoreFrontend::Write(
     AttachmentStore::Component component,
     const AttachmentList& attachments,
     const AttachmentStore::WriteCallback& callback) {
-  DCHECK(CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   backend_task_runner_->PostTask(
       FROM_HERE, base::Bind(&AttachmentStoreBackend::Write,
                             base::Unretained(backend_.get()), component,
@@ -71,7 +72,7 @@ void AttachmentStoreFrontend::Write(
 
 void AttachmentStoreFrontend::SetReference(AttachmentStore::Component component,
                                            const AttachmentIdList& ids) {
-  DCHECK(CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   backend_task_runner_->PostTask(
       FROM_HERE, base::Bind(&AttachmentStoreBackend::SetReference,
                             base::Unretained(backend_.get()), component, ids));
@@ -81,7 +82,7 @@ void AttachmentStoreFrontend::DropReference(
     AttachmentStore::Component component,
     const AttachmentIdList& ids,
     const AttachmentStore::DropCallback& callback) {
-  DCHECK(CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   backend_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&AttachmentStoreBackend::DropReference,
@@ -92,7 +93,7 @@ void AttachmentStoreFrontend::ReadMetadataById(
     AttachmentStore::Component component,
     const AttachmentIdList& ids,
     const AttachmentStore::ReadMetadataCallback& callback) {
-  DCHECK(CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   backend_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&AttachmentStoreBackend::ReadMetadataById,
@@ -102,7 +103,7 @@ void AttachmentStoreFrontend::ReadMetadataById(
 void AttachmentStoreFrontend::ReadMetadata(
     AttachmentStore::Component component,
     const AttachmentStore::ReadMetadataCallback& callback) {
-  DCHECK(CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   backend_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&AttachmentStoreBackend::ReadMetadata,