Store attachment crc in AttachmentStore

sync/api/attachments/attachment.h

Index: sync/api/attachments/attachment.h
diff --git a/sync/api/attachments/attachment.h b/sync/api/attachments/attachment.h
index af4c36da70b0f71eb8393c03fc0fa89074d7265d..cb9d12ca51f84c23cd173ed9f35f9b0f8afa8c0a 100644
--- a/sync/api/attachments/attachment.h
+++ b/sync/api/attachments/attachment.h
@@ -32,15 +32,17 @@ class SYNC_EXPORT Attachment {
   // Creates an attachment with a unique id and the supplied data.
   //
   // Used when creating a brand new attachment.
-  static Attachment Create(const scoped_refptr<base::RefCountedMemory>& data);
+  static Attachment CreateNew(
+      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 Attachment CreateWithId(
+  static Attachment RestoreExisting(
       const AttachmentId& id,
-      const scoped_refptr<base::RefCountedMemory>& data);
+      const scoped_refptr<base::RefCountedMemory>& data,
+      uint32_t crc32c);
 
   // Returns this attachment's id.
   const AttachmentId& GetId() const;
@@ -48,12 +50,16 @@ class SYNC_EXPORT Attachment {
   // Returns this attachment's data.
   const scoped_refptr<base::RefCountedMemory>& GetData() const;
 
+  uint32_t GetCrc32c() const;

[maniscalco, 2014/11/11 00:44:53]

Maybe indicate that this is a cheap operation?

e.g.

// Returns the pre-computed CRC32C for the attachment.

[pavely, 2014/11/11 22:27:14]

Done.

+
  private:
   AttachmentId id_;
   scoped_refptr<base::RefCountedMemory> data_;
+  uint32_t crc32c_;
 
   Attachment(const AttachmentId& id,
-             const scoped_refptr<base::RefCountedMemory>& data);
+             const scoped_refptr<base::RefCountedMemory>& data,
+             uint32_t crc32c);
 };
 
 typedef std::vector<syncer::Attachment> AttachmentList;