blob_handler: provide a convenience static factory

Provide a static factory for convenience to get a unique_ptr to the base
object.

Change-Id: I058e7a28a6bc30182ed9ada5ea479a317d071893
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/src/ipmiblob/blob_handler.hpp b/src/ipmiblob/blob_handler.hpp
index 6c4ba7a..0b6db17 100644
--- a/src/ipmiblob/blob_handler.hpp
+++ b/src/ipmiblob/blob_handler.hpp
@@ -26,6 +26,15 @@
         bmcBlobWriteMeta = 10,
     };
 
+    /**
+     * Create a BlobInterface pointer for use given an ipmi handler.
+     *
+     * @note This is a convenience method.
+     * @return a BlobHandler wrapped as a BlobInterface pointer.
+     */
+    static std::unique_ptr<BlobInterface>
+        CreateBlobHandler(std::unique_ptr<IpmiInterface> ipmi);
+
     explicit BlobHandler(std::unique_ptr<IpmiInterface> ipmi) :
         ipmi(std::move(ipmi)){};