Fixes #11357: Vertically center sm and xs buttons in the navbar

dist/css/bootstrap.css

@@ -4671,6 +4671,16 @@ textarea.input-group-sm > .input-group-btn > .btn {
   margin-bottom: 8px;
 }
 
+.navbar-btn.btn-sm {
+  margin-top: 10px;
+  margin-bottom: 10px;
+}
+
+.navbar-btn.btn-xs {
+  margin-top: 14px;
+  margin-bottom: 14px;
+}
+
 .navbar-text {
   margin-top: 15px;
   margin-bottom: 15px;

less/navbar.less

@@ -333,6 +333,13 @@
 
 .navbar-btn {
   .navbar-vertical-align(@input-height-base);
+
+  &.btn-sm {
+    .navbar-vertical-align(@input-height-small);
+  }
+  &.btn-xs {
+    .navbar-vertical-align(22);
+  }
 }