Implementation of OnDiskAttachmentStore.

sync/api/attachments/attachment_store.h

Index: sync/api/attachments/attachment_store.h
diff --git a/sync/api/attachments/attachment_store.h b/sync/api/attachments/attachment_store.h
index 45ccaf9c8efa355eaa53862eaf89463fc86c97eb..e4da08fa5964d2a38bb44111ef5a311e39f5f6b4 100644
--- a/sync/api/attachments/attachment_store.h
+++ b/sync/api/attachments/attachment_store.h
@@ -13,6 +13,7 @@
 #include "sync/base/sync_export.h"
 
 namespace base {
+class FilePath;
 class RefCountedMemory;
 }  // namespace base
 
@@ -35,6 +36,7 @@ class SYNC_EXPORT AttachmentStoreBase {
     UNSPECIFIED_ERROR,  // An unspecified error occurred for one or more items.
   };
 
+  typedef base::Callback<void(const Result&)> LoadCallback;
   typedef base::Callback<void(const Result&,
                               scoped_ptr<AttachmentMap>,
                               scoped_ptr<AttachmentIdList>)> ReadCallback;
@@ -44,6 +46,13 @@ class SYNC_EXPORT AttachmentStoreBase {
   AttachmentStoreBase();
   virtual ~AttachmentStoreBase();
 
+  // Asynchronously loads attachment store.
+  //
+  // |callback| will be invoked once AttachmentStore is loaded. If |callback|'s
+  // result is SUCCESS store is ready for operations. Otherwise result will be
+  // UNSPECIFIED_ERROR.
+  virtual void Load(const LoadCallback& callback) = 0;

[maniscalco, 2014/10/14 21:03:18]

What's the workflow here?  Call a Create method, then Load?  Is it illegal to
call Read/Write/Drop before Load completes successfully?

I wonder if there's a better name for this method.  When I see Load, I wonder
how it's different from Read.  Would this be better described as Open?

[pavely, 2014/10/16 22:13:29]

Removed method altogether.

+
   // Asynchronously reads the attachments identified by |ids|.
   //
   // |callback| will be invoked when finished. AttachmentStore will attempt to
@@ -96,6 +105,9 @@ class SYNC_EXPORT AttachmentStore
   // attachment store. For now frontend lives on the same thread as backend.
   static scoped_refptr<AttachmentStore> CreateInMemoryStore();
 
+  static scoped_refptr<AttachmentStore> CreateOnDiskStore(

[maniscalco, 2014/10/14 21:03:18]

Can you please document this method?

[pavely, 2014/10/16 22:13:29]

Done.

+      const base::FilePath& path);
+
  protected:
   friend class base::RefCountedThreadSafe<AttachmentStore>;
   virtual ~AttachmentStore();