slideshow::update fontsize and text intent

resolve:
    set iframe body lang same as installer lang

tower:https://tower.im/projects/8a6342c556be4c4eb898fdd7fd6fcb2f/todos/b04853e08fce41cea296ebf05d7f4437/
tower:https://tower.im/projects/8a6342c556be4c4eb898fdd7fd6fcb2f/todos/eac334d13d5b40428732a9a958ae9a6f/

Change-Id: I0fafe77906d8e9dbee5cadd4c79d21652b7ec611