mips scale optimization BUG=126 TEST=NONE Review URL: https://webrtc-codereview.appspot.com/918005
mips scale optimization
BUG=126
TEST=NONE
Review URL: https://webrtc-codereview.appspot.com/918005
flykickbird/libyuv,flykickbird/libyuv,flykickbird/libyuv