I don't know what is the issue with the libvpx repository, but when using the JHBUILD_MIRROR feature <https://trac.webkit.org/changeset/166061> it sometimes takes ages to run the fetch operation or it even fails with a network timeout.
And, I see no reason to use the git repository.
Using a release tarball should be better in any case and will lower the disk and network needs required for building WebKitGTK.
Created attachment 306134 [details]
Thanks for the review.
I'm landing it with a minor diff to use the variable version on the filename.
- <branch repo="downloads.webmproject.org"
- module="libvpx-1.6.0.tar.bz2" version="1.6.0"
+ <branch version="1.6.0"
Committed r214854: <http://trac.webkit.org/changeset/214854>