GD: use one source as init_flag

Add ffi for needed method and remove duplicate parsing in c++

Test: cargo test init_flags
Bug: 251328572
Tag: #refactor
Merged-In: Id5f60e7ac2834e71783787b4c2af70c9581f5d40
Change-Id: Id5f60e7ac2834e71783787b4c2af70c9581f5d40
(cherry picked from commit 66b626e1)