Summary:
Changelog:
[ios][added] - introduce MockSurfaceHandler
following the recommendation in https://fb.workplace.com/groups/474291069286180/posts/6540719469309946
in order to unit test classes that use SurfaceHandler, we need to be able to mock it somehow - since the class is final we aren't able to do that. in this diff, we add the mock class.
Reviewed By: sammy-SC
Differential Revision: D30578927
fbshipit-source-id: 9b39b03ad0b55cecd9b482f9cce9630d7e7d5bda
Phillip Pan