Merge pull request #8408 from cvrebert/progress-bar-variant-mixin

extract .progress-bar-variant mix-in

less/mixins.less

@@ -427,6 +427,15 @@
   margin-bottom: ((@navbar-height - @element-height) / 2);
 }
 
+// Progress bars
+// -------------------------
+.progress-bar-variant(@color) {
+  background-color: @color;
+  .progress-striped & {
+    #gradient > .striped(@color);
+  }
+}
+
 // Responsive utilities
 // -------------------------
 // More easily include all the states for responsive-utilities.less.

less/progress-bars.less

@@ -87,32 +87,20 @@
 
 // Danger (red)
 .progress-bar-danger {
-  background-color: @progress-bar-danger-bg;
-  .progress-striped & {
-    #gradient > .striped(@progress-bar-danger-bg);
-  }
+  .progress-bar-variant(@progress-bar-danger-bg);
 }
 
 // Success (green)
 .progress-bar-success {
-  background-color: @progress-bar-success-bg;
-  .progress-striped & {
-    #gradient > .striped(@progress-bar-success-bg);
-  }
+  .progress-bar-variant(@progress-bar-success-bg);
 }
 
 // Warning (orange)
 .progress-bar-warning {
-  background-color: @progress-bar-warning-bg;
-  .progress-striped & {
-    #gradient > .striped(@progress-bar-warning-bg);
-  }
+  .progress-bar-variant(@progress-bar-warning-bg);
 }
 
 // Info (teal)
 .progress-bar-info {
-  background-color: @progress-bar-info-bg;
-  .progress-striped & {
-    #gradient > .striped(@progress-bar-info-bg);
-  }
+  .progress-bar-variant(@progress-bar-info-bg);
 }