Fix combined checksum calculation to use isa. am: 539d38c
am: 6b64d4b

* commit '6b64d4b89c2d0282d8a0af8d20a4c138a9bbf257':
  Fix combined checksum calculation to use isa.

Change-Id: I870e1915bfcb85f7890682a3b686d141f9eb13a1