iOS9.3beta3,PHImageManagerrequestImageDataForAsset返回指向照片的imageData，尽管PHAssert是在设备上捕获的视频Assets。文档says:"requestImageDataForAsset(_:options:resultHandler:)...IftheversionoptionissettoPHImageRequestOptionsVersionCurrent,Photosprovidesrenderedimagedata,includingtheresultsofanyeditsthathavebeenmadetot