more generated files from chromium to ignore since roll
more generated files from chromium to ignore since roll

R=harryjin@google.com, harryjin
BUG=none

Review URL: https://webrtc-codereview.appspot.com/52159004.

lemenkov/libyuv,lemenkov/libyuv,yarrcc/libyuv-ios,yarrcc/libyuv-ios,lemenkov/libyuv,lemenkov/libyuv,disigma/yuv,disigma/yuv,disigma/yuv,yarrcc/libyuv-ios,yarrcc/libyuv-ios