Add AttachmentDownloader interface, change signature of AttachmentStore::Read

sync/internal_api/attachments/fake_attachment_store.cc

 // 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/fake_attachment_store.h"
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/memory/ref_counted_memory.h"
 #include "base/message_loop/message_loop_proxy.h"
@@ skipping 29 matching lines @@
     : frontend_task_runner_(frontend_task_runner) {}
 
 FakeAttachmentStore::Backend::~Backend() {}
 
 void FakeAttachmentStore::Backend::Read(const AttachmentIdList& ids,
                                         const ReadCallback& callback) {
   Result result_code = SUCCESS;
   AttachmentIdList::const_iterator id_iter = ids.begin();
   AttachmentIdList::const_iterator id_end = ids.end();
   scoped_ptr<AttachmentMap> result_map(new AttachmentMap);
+  scoped_ptr<AttachmentIdList> unavailable_attachments(new AttachmentIdList);
   for (; id_iter != id_end; ++id_iter) {
     const AttachmentId& id = *id_iter;
     syncer::AttachmentMap::iterator attachment_iter =
         attachments_.find(*id_iter);
     if (attachment_iter != attachments_.end()) {
       const Attachment& attachment = attachment_iter->second;
       result_map->insert(std::make_pair(id, attachment));
     } else {
-      result_code = UNSPECIFIED_ERROR;
-      break;
+      unavailable_attachments->push_back(id);
     }
   }
+  if (!unavailable_attachments->empty()) {
+    result_code = UNSPECIFIED_ERROR;
+  }
   frontend_task_runner_->PostTask(
-      FROM_HERE, base::Bind(callback, result_code, base::Passed(&result_map)));
+      FROM_HERE,
+      base::Bind(callback,
+                 result_code,
+                 base::Passed(&result_map),
+                 base::Passed(&unavailable_attachments)));
 }
 
 void FakeAttachmentStore::Backend::Write(const AttachmentList& attachments,
                                          const WriteCallback& callback) {
   AttachmentList::const_iterator iter = attachments.begin();
   AttachmentList::const_iterator end = attachments.end();
   for (; iter != end; ++iter) {
     attachments_.insert(std::make_pair(iter->GetId(), *iter));
   }
   frontend_task_runner_->PostTask(FROM_HERE, base::Bind(callback, SUCCESS));
@@ skipping 38 matching lines @@
 }
 
 void FakeAttachmentStore::Drop(const AttachmentIdList& ids,
                                const DropCallback& callback) {
   backend_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&FakeAttachmentStore::Backend::Drop, backend_, ids, callback));
 }
 
 }  // namespace syncer