[gtk+] Fix another reftest

[Matthias Clasen <matthiasc src gnome org>]

commit 27b4bfc1cf273c922cedba59ca2b03169070222a
Author: Matthias Clasen <mclasen redhat com>
Date:   Sat Jan 30 21:43:49 2016 -0500

    Fix another reftest
    
    Make sure the notebook in the separator-size reftest does not
    peek through, by giving it a transparent background.

 testsuite/reftests/Makefile.am        |    1 +
 testsuite/reftests/separator-size.css |    3 +++
 2 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/testsuite/reftests/Makefile.am b/testsuite/reftests/Makefile.am
index 44d5c55..89d89e0 100644
--- a/testsuite/reftests/Makefile.am
+++ b/testsuite/reftests/Makefile.am
@@ -380,6 +380,7 @@ testdata = \
        revealer-wrappable-contents.ui \
        rotated-layout.ref.ui \
        rotated-layout.ui \
+       separator-size.css \
        separator-size.ref.ui \
        separator-size.ui \
        set-default-direction.ui \
diff --git a/testsuite/reftests/separator-size.css b/testsuite/reftests/separator-size.css
new file mode 100644
index 0000000..2dff874
--- /dev/null
+++ b/testsuite/reftests/separator-size.css
@@ -0,0 +1,3 @@
+notebook stack {
+  background: none;
+}