Update sync API to support attachments.

sync/api/attachments/attachment.h

 // 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.
 
 #ifndef SYNC_API_ATTACHMENTS_ATTACHMENT_H_
 #define SYNC_API_ATTACHMENTS_ATTACHMENT_H_
 
 #include "base/basictypes.h"
 #include "base/gtest_prod_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/ref_counted_memory.h"
 #include "base/memory/scoped_ptr.h"
 #include "sync/base/sync_export.h"
 #include "sync/protocol/sync.pb.h"
 
 namespace syncer {
 
 // A blob of in-memory data attached to a sync item.
 //
 // While Attachment objects themselves aren't immutable (they are assignable)
 // the data they wrap is immutable.
 //
 // It is cheap to copy Attachments. Feel free to store and return by value.
 class SYNC_EXPORT Attachment {
  public:
   ~Attachment();
 
   // Default copy and assignment are welcome.
 
+  // Creates a unique attachment id.
+  static sync_pb::AttachmentId CreateId();
+
   // Creates an attachment with a unique id and the supplied data.
   //
   // Used when creating a brand new attachment.
-  static scoped_ptr<Attachment> Create(
-      const scoped_refptr<base::RefCountedMemory>& data);
+  static Attachment Create(const scoped_refptr<base::RefCountedMemory>& data);
 
   // Creates an attachment with the supplied id and data.
   //
   // Used when you want to recreate a specific attachment. E.g. creating a local
   // copy of an attachment that already exists on the sync server.
-  static scoped_ptr<Attachment> CreateWithId(
+  static Attachment CreateWithId(
       const sync_pb::AttachmentId& id,
       const scoped_refptr<base::RefCountedMemory>& data);
 
   // Returns this attachment's id.
   const sync_pb::AttachmentId& GetId() const;
 
   // Returns this attachment's data.
   const scoped_refptr<base::RefCountedMemory>& GetData() const;
 
  private:
   sync_pb::AttachmentId id_;
   scoped_refptr<base::RefCountedMemory> data_;
 
-  friend class AttachmentTest;
-  FRIEND_TEST_ALL_PREFIXES(AttachmentTest, CreateId_UniqueIdIsUnique);
-
   Attachment(const sync_pb::AttachmentId& id,
              const scoped_refptr<base::RefCountedMemory>& data);
-
-  // Creates a unique attachment id.
-  static sync_pb::AttachmentId CreateId();
 };
 
 typedef std::vector<syncer::Attachment> AttachmentList;
 typedef std::string AttachmentIdUniqueId;  // AttachmentId.unique_id()
 typedef std::map<AttachmentIdUniqueId, Attachment> AttachmentMap;
 typedef std::vector<sync_pb::AttachmentId> AttachmentIdList;
 
 }  // namespace syncer
 
 #endif  // SYNC_API_ATTACHMENTS_ATTACHMENT_H_