reuse inline styles as a mixin

www/contacts/main.less

@@ -149,11 +149,7 @@ body {
         align-items: center;
         height: 50px;
 
-        .avatar,
+        .hover () {
-        .right-col {
-             flex:1 1 auto;
-        }
-        .remove-history {
             height: 100%;
             line-height: 30px;
             padding: 10px;
@@ -161,9 +157,20 @@ body {
                 background-color: rgba(50,50,50,0.3);
             }
         }
+
+        .avatar,
+        .right-col {
+             flex:1 1 auto;
+        }
+        .remove-history {
+            .hover;
+        }
         .avatar {
             margin: 10px;
         }
+        .more-history {
+            .hover;
+        }
     }
     .chat {
         height: 100%;