Deprecate NonThreadSafe in components/sync in favor of SequenceChecker.

components/sync/engine/attachments/fake_attachment_uploader.h

Index: components/sync/engine/attachments/fake_attachment_uploader.h
diff --git a/components/sync/engine/attachments/fake_attachment_uploader.h b/components/sync/engine/attachments/fake_attachment_uploader.h
index b6e4ecdba91b44d7f2ab04c80ed0ca383d895ce9..6e8d11473830603049b44b30244374a258abdc26 100644
--- a/components/sync/engine/attachments/fake_attachment_uploader.h
+++ b/components/sync/engine/attachments/fake_attachment_uploader.h
@@ -6,14 +6,13 @@
 #define COMPONENTS_SYNC_ENGINE_ATTACHMENTS_FAKE_ATTACHMENT_UPLOADER_H_
 
 #include "base/macros.h"
-#include "base/threading/non_thread_safe.h"
+#include "base/sequence_checker.h"
 #include "components/sync/engine/attachments/attachment_uploader.h"
 
 namespace syncer {
 
 // A fake implementation of AttachmentUploader.
-class FakeAttachmentUploader : public AttachmentUploader,
-                               public base::NonThreadSafe {
+class FakeAttachmentUploader : public AttachmentUploader {
  public:
   FakeAttachmentUploader();
   ~FakeAttachmentUploader() override;
@@ -23,6 +22,8 @@ class FakeAttachmentUploader : public AttachmentUploader,
                         const UploadCallback& callback) override;
 
  private:
+  SEQUENCE_CHECKER(sequence_checker_);
+
   DISALLOW_COPY_AND_ASSIGN(FakeAttachmentUploader);
 };