Evolution selection is white-on-white in GNOME 3.20

[Paul Smith]

This morning I updated my Ubuntu GNOME 16.04 LTS system to GNOME 3.20
using the Gnome3 Staging PPA.

One issue is that now when I select text in Evolution (the message
preview/reader window and also the compose window), the selection is
white-on-white so the text just disappears while the selection is
active.  If I select text in another GNOME application like gedit, it's
the expected blue background/white foreground.

There was an email thread on the evolution mailing list about this
issue, from someone using Debian.  Here's a link to the relevant thread:

https://mail.gnome.org/archives/evolution-list/2016-May/msg00045.html

Here's a note from Milan in that (long) thread that explains the issue:

https://mail.gnome.org/archives/evolution-list/2016-May/msg00091.html

Basically, there is conditionally-compiled code in WebKitGTK+ such that
if it's compiled against an older gtk+ 3.18, then the code needed to get
selection working right is not compiled.

We need to get WebKitGTK+ to be compiled against gtk+ 3.20, in order for
this issue to be fixed and selection to work properly.

There's a Debian bug filed:

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=825304

Is there a good way to get a new build of WebKitGTK+ compiled against
gtk+ 3.20, for the GNOME3 Staging PPA?

Cheers!