mojom.gni: Set deps correctly on generated C++ source sets
mojom.gni: Set deps correctly on generated C++ source sets

These targets need to depend on the generated C++ source sets corresponding to
the mojom target's dependencies.

R=yzshen@chromium.org

Review URL: https://codereview.chromium.org/1100943002

chinmaygarde/mojo,collinjackson/mojo,collinjackson/mojo,jianglu/mojo,chinmaygarde/mojo,chinmaygarde/mojo,jianglu/mojo,afandria/mojo,collinjackson/mojo,chinmaygarde/mojo,chinmaygarde/mojo,jianglu/mojo,collinjackson/mojo,collinjackson/mojo,afandria/mojo,afandria/mojo,afandria/mojo,afandria/mojo,afandria/mojo,chinmaygarde/mojo,jianglu/mojo,collinjackson/mojo,chinmaygarde/mojo,afandria/mojo,collinjackson/mojo,jianglu/mojo,chinmaygarde/mojo,jianglu/mojo,jianglu/mojo,collinjackson/mojo,afandria/mojo,jianglu/mojo,chinmaygarde/mojo,collinjackson/mojo