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

sync/internal_api/attachments/attachment_service_proxy_unittest.cc

Index: sync/internal_api/attachments/attachment_service_proxy_unittest.cc
diff --git a/sync/internal_api/attachments/attachment_service_proxy_unittest.cc b/sync/internal_api/attachments/attachment_service_proxy_unittest.cc
index a66b39f4858fc278c327bab10a694319a529e5d2..41af1b233710914b1e42caf3cd25a96c9f6727b2 100644
--- a/sync/internal_api/attachments/attachment_service_proxy_unittest.cc
+++ b/sync/internal_api/attachments/attachment_service_proxy_unittest.cc
@@ -32,6 +32,8 @@
   }
 
   ~StubAttachmentService() override {}
+
+  AttachmentStore* GetStore() override { return NULL; }
 
   void GetOrDownloadAttachments(
       const AttachmentIdList& attachment_ids,
@@ -130,6 +132,10 @@
   int count_callback_get_or_download;
 };
 
+TEST_F(AttachmentServiceProxyTest, GetStore) {
+  EXPECT_EQ(NULL, proxy->GetStore());
+}
+
 // Verify that each of AttachmentServiceProxy's methods are invoked on the stub.
 // Verify that the methods that take callbacks invoke passed callbacks on this
 // thread.