[gnome-builder] page: add styling for overview map

[Christian Hergert <chergert src gnome org>]

commit 2e9046cde50aed3b7447d0968517149aa1a8aae7
Author: Christian Hergert <chergert redhat com>
Date:   Tue Oct 12 17:41:56 2021 -0700

    page: add styling for overview map

 src/libide/editor/ide-editor-page.ui              | 3 +++
 src/libide/themes/themes/shared/shared-editor.css | 4 ++++
 2 files changed, 7 insertions(+)
---
diff --git a/src/libide/editor/ide-editor-page.ui b/src/libide/editor/ide-editor-page.ui
index 1306575bc..7a4227383 100644
--- a/src/libide/editor/ide-editor-page.ui
+++ b/src/libide/editor/ide-editor-page.ui
@@ -114,6 +114,9 @@
             <child>
               <object class="GtkSourceMap" id="map">
                 <property name="visible">false</property>
+                <style>
+                  <class name="source-map"/>
+                </style>
               </object>
             </child>
           </object>
diff --git a/src/libide/themes/themes/shared/shared-editor.css 
b/src/libide/themes/themes/shared/shared-editor.css
index 20650c901..a776ee214 100644
--- a/src/libide/themes/themes/shared/shared-editor.css
+++ b/src/libide/themes/themes/shared/shared-editor.css
@@ -147,3 +147,7 @@ vte-terminal {
   background-color: @content_view_bg;
   color: @theme_fg_color;
 }
+
+textview.source-map .scrubber {
+  border-radius: 9px;
+}