This CL removes the ability to load remote font faces using CSS. This CL is
part of a series to remove the network dependency from Sky engine. We'll likely
add the ability to load custom fonts in the future, but we'll base the API on
mojo::DataPipe, similar to how we load images over mojo::DataPipes today.
TBR=eseidel@google.com
Review URL: https://codereview.chromium.org/1223843003.
df78625631