BUG=libyuv:699
TESTED=LibYUVConvertTest.I420ToARGB_RGB565_Opt

Change-Id: I87943bcad056fbbe051301f45c7dc0ae0620c837
Reviewed-on: https://chromium-review.googlesource.com/478578Reviewed-by: Frank Barchard <fbarchard@google.com>
Commit-Queue: Frank Barchard <fbarchard@google.com>