[meld] Update LinkMap CSS selector

[Kai Willadsen <kaiw src gnome org>]

commit 4e17a7d307cdf7cfde0f6cc838ee3448e4efa90d
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Sun Jan 31 07:58:30 2016 +1000

    Update LinkMap CSS selector

 bin/meld        |    2 +-
 data/meld.css   |    2 +-
 meld/linkmap.py |    6 ++++++
 3 files changed, 8 insertions(+), 2 deletions(-)
---
diff --git a/bin/meld b/bin/meld
index 324758d..aba1ff2 100755
--- a/bin/meld
+++ b/bin/meld
@@ -212,7 +212,7 @@ def setup_resources():
     bg_colour = textview_context.get_background_color(
         textview_context.get_state())
     textview_context.restore()
-    linkmap_css = "LinkMap { background-color: %s; }" % bg_colour.to_string()
+    linkmap_css = "link-map { background-color: %s; }" % bg_colour.to_string()
     linkmap_provider = Gtk.CssProvider()
     linkmap_provider.load_from_data(linkmap_css)
     Gtk.StyleContext.add_provider_for_screen(
diff --git a/data/meld.css b/data/meld.css
index 8aa1251..f121dbb 100644
--- a/data/meld.css
+++ b/data/meld.css
@@ -10,7 +10,7 @@
     padding: 3px 2px 2px 2px;
 }
 
-LinkMap {
+link-map {
     border-width: 0 0 1px 0;
     border-style: solid;
     border-color: @borders;
diff --git a/meld/linkmap.py b/meld/linkmap.py
index f7c11f0..47b3dea 100644
--- a/meld/linkmap.py
+++ b/meld/linkmap.py
@@ -127,6 +127,12 @@ class LinkMap(Gtk.DrawingArea):
     def do_scroll_event(self, event):
         self.filediff.next_diff(event.direction)
 
+try:
+    LinkMap.set_css_name("link-map")
+except AttributeError:
+    # New API in 3.20
+    pass
+
 
 class ScrollLinkMap(Gtk.DrawingArea):