The DEPS entry for gflags added in https://codereview.chromium.org/1413723002/
assumed the Chromium/WebRTC checkout layout with 'src' as the
top-directory name. That doesn't work for libyuv, since the top-directory
is named 'libyuv'.

BUG=libyuv:507

Review URL: https://codereview.chromium.org/1410673004 .