Fix unit test break caused by outdated mocks.
Fix unit test break caused by outdated mocks.

Update mock functions AssetManager::LoadShader and Texture::Finalize.
PiperOrigin-RevId: 139966365
Change-Id: I5c48b424b852d64435e68a68ac04ac2d4111b41f

google/flatui,google/flatui,google/flatui,google/flatui