Use the aom_writer type rather than the tag in calling code.

This makes room for typedefing some other struct to aom_writer.

Change-Id: I1e82de1320da00b3e41c90b14f2df45e7628aa89
(cherry picked from commit d69161f8f1eed602e0e5d21f4e6157b674e30cf6)
1 file changed