firmware: add active blob ids

Add blob ids that correspond to an active image upload (static or ubi),
or an active hash upload.

Change-Id: Ieff082c780666ca2fa3eec9fad928437a6c1c2cb
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/firmware_handler.cpp b/firmware_handler.cpp
index 9bcdd39..b828002 100644
--- a/firmware_handler.cpp
+++ b/firmware_handler.cpp
@@ -10,6 +10,9 @@
 {
 
 const std::string FirmwareBlobHandler::hashBlobID = "/flash/hash";
+const std::string FirmwareBlobHandler::activeImageBlobID =
+    "/flash/active/image";
+const std::string FirmwareBlobHandler::activeHashBlobID = "/flash/active/hash";
 
 std::unique_ptr<GenericBlobInterface>
     FirmwareBlobHandler::CreateFirmwareBlobHandler(