[meld/ui-next] Override Adwaita's very odd notebook child background setting

[Kai Willadsen <kaiw src gnome org>]

commit a6d4c07b6869c622ce06047d8f5fee09ba290e37
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Sat Mar 23 08:23:58 2019 +1000

    Override Adwaita's very odd notebook child background setting

 data/meld.css                 | 6 +++++-
 meld/resources/ui/filediff.ui | 3 ---
 2 files changed, 5 insertions(+), 4 deletions(-)
---
diff --git a/data/meld.css b/data/meld.css
index 709e641c..10588759 100644
--- a/data/meld.css
+++ b/data/meld.css
@@ -47,7 +47,11 @@ meld-find-bar {
     border-color: @borders;
 }
 
-.meld-notebook-child {
+/* Default Adwaita notebook styling gives a much lighter background to
+ * notebook children when there's more than one, but we definitely don't
+ * want this.
+ */
+.meld-notebook > stack:not(:only-child) {
     background-color: @theme_bg_color;
 }
 
diff --git a/meld/resources/ui/filediff.ui b/meld/resources/ui/filediff.ui
index 8f13a1c9..bd067311 100644
--- a/meld/resources/ui/filediff.ui
+++ b/meld/resources/ui/filediff.ui
@@ -12,9 +12,6 @@
       <object class="DiffGrid" id="grid">
         <property name="visible">True</property>
         <property name="can_focus">False</property>
-        <style>
-          <class name="meld-notebook-child"/>
-        </style>
         <child>
           <object class="GtkToolbar" id="file_toolbar2">
             <property name="visible">True</property>