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

In this change:
- Move towards following class hierarchy: http://www.plantuml.com:80/plantuml/png/ZPBTJiCm38NlynIvv4TzWsaI525nCI5jkw-on1EZQHmvwQG9U7TC4-ZeKiITvNm-EiSExbv1Hxc6VOszYs24mDHQeG6xFNcGRqBAknYLVkd0nKr40l7nmqrU1deDeRUHYrfPkrEw3LmJx848YCkWqODfkECZBIOAZuHin9abWxUo9b0Hdjt38RGJyEhwZ4YZI9kJq_mmRp0pAPKnd7pGgG8t6usTHyVe7_FPtY3mbOth9ghGDjGxTnwlaEq-ySjv-KmCwZflxvVyE5bSIa4Mw7ZGyDHvAyHurPkgkhZgz9PuoNp75tDhAUZcJ68cwkATHyfXnFWn4_PFDsKuNLuKLrFodGS-0G00
- Remove AttachmenService::GetStore. Now attachment store is owned by
  model type, there is no need to get it from AttachmentService
- Introduce AttachmentReferrer. There is no functionality behind it yet
  and interface is not complete for it. These will come in the next change.

BUG=457735
R=maniscalco@chromium.org
TEST=Not exposed in chrome. Only unit tests available (sync_unit_tests)

Review URL: https://codereview.chromium.org/986743004

Cr-Commit-Position: refs/heads/master@{#319733}

1 files changed, 3 insertions, 3 deletions

diff --git a/components/sync_driver/generic_change_processor.cc b/components/sync_driver/generic_change_processor.cc
index 60d9977..8f3eff1 100644
--- a/components/sync_driver/generic_change_processor.cc
+++ b/components/sync_driver/generic_change_processor.cc
@@ -94,7 +94,7 @@ GenericChangeProcessor::GenericChangeProcessor(
     const base::WeakPtr<syncer::SyncMergeResult>& merge_result,
     syncer::UserShare* user_share,
     SyncApiComponentFactory* sync_factory,
-    const scoped_refptr<syncer::AttachmentStore>& attachment_store)
+    scoped_ptr<syncer::AttachmentStore> attachment_store)
     : ChangeProcessor(error_handler),
       type_(type),
       local_service_(local_service),
@@ -103,14 +103,14 @@ GenericChangeProcessor::GenericChangeProcessor(
       weak_ptr_factory_(this) {
   DCHECK(CalledOnValidThread());
   DCHECK_NE(type_, syncer::UNSPECIFIED);
-  if (attachment_store.get()) {
+  if (attachment_store) {
     std::string store_birthday;
     {
       syncer::ReadTransaction trans(FROM_HERE, share_handle());
       store_birthday = trans.GetStoreBirthday();
     }
     attachment_service_ = sync_factory->CreateAttachmentService(
-        attachment_store, *user_share, store_birthday, type, this);
+        attachment_store.Pass(), *user_share, store_birthday, type, this);
     attachment_service_weak_ptr_factory_.reset(
         new base::WeakPtrFactory<syncer::AttachmentService>(
             attachment_service_.get()));