[gxml] CssSelectorParser.match() implement E[prop="bar"]

[Daniel Espinosa Ortiz <despinosa src gnome org>]

commit 14e6f4939cb3fdb3fc4ac5c7e7080ef964df2b5f
Author: Daniel Espinosa <esodan gmail com>
Date:   Wed Sep 6 08:25:56 2017 -0700

    CssSelectorParser.match() implement E[prop="bar"]

 gxml/css-selector-parser.vala |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)
---
diff --git a/gxml/css-selector-parser.vala b/gxml/css-selector-parser.vala
index 298fa94..fe13dd3 100644
--- a/gxml/css-selector-parser.vala
+++ b/gxml/css-selector-parser.vala
@@ -324,6 +324,11 @@ public class GXml.CssSelectorParser : GLib.Object {
                                var p = element.get_attribute (s.data);
                                if (p != null) return true;
                        }
+                       if (is_element && s.selector_type == CssSelectorType.ATTRIBUTE_EQUAL) {
+                               var p = element.get_attribute (s.data);
+                               if (p == null) return false;
+                               if (p == s.value) return true;
+                       }
                }
                return false;
        }