[Sync] Add size and crc32c to AttachmentId.

sync/internal_api/attachments/on_disk_attachment_store.cc

Index: sync/internal_api/attachments/on_disk_attachment_store.cc
diff --git a/sync/internal_api/attachments/on_disk_attachment_store.cc b/sync/internal_api/attachments/on_disk_attachment_store.cc
index ec6fc75931bd9283d50033f4b055f9f52f514717..699e1f5add122106a7f7030881e3c9731d295c2d 100644
--- a/sync/internal_api/attachments/on_disk_attachment_store.cc
+++ b/sync/internal_api/attachments/on_disk_attachment_store.cc
@@ -319,12 +319,18 @@ scoped_ptr<Attachment> OnDiskAttachmentStore::ReadSingleAttachment(
   scoped_refptr<base::RefCountedMemory> data =
       base::RefCountedString::TakeString(&data_str);
   uint32_t crc32c = ComputeCrc32c(data);
-  if (record_metadata.has_crc32c() && record_metadata.crc32c() != crc32c) {
-    DVLOG(1) << "Attachment crc does not match";
-    return attachment.Pass();
+  if (record_metadata.has_crc32c()) {
+    if (record_metadata.crc32c() != crc32c) {
+      DVLOG(1) << "Attachment crc32c does not match value read from store";
+      return attachment.Pass();
+    }
+    if (record_metadata.crc32c() != attachment_id.GetCrc32c()) {
+      DVLOG(1) << "Attachment crc32c does not match value in AttachmentId";
+      return attachment.Pass();
+    }
   }
   attachment.reset(
-      new Attachment(Attachment::CreateFromParts(attachment_id, data, crc32c)));
+      new Attachment(Attachment::CreateFromParts(attachment_id, data)));
   return attachment.Pass();
 }