[MD settings] support RTL in paper-slider

third_party/polymer/v1_0/components-chromium/paper-slider/paper-slider.html

Index: third_party/polymer/v1_0/components-chromium/paper-slider/paper-slider.html
diff --git a/third_party/polymer/v1_0/components-chromium/paper-slider/paper-slider.html b/third_party/polymer/v1_0/components-chromium/paper-slider/paper-slider.html
index a53a0bbb4b53827c8f6e26acbbd98a26c3ba7a72..4a3239d27141262dcadc945c514baa82009023e0 100644
--- a/third_party/polymer/v1_0/components-chromium/paper-slider/paper-slider.html
+++ b/third_party/polymer/v1_0/components-chromium/paper-slider/paper-slider.html
@@ -89,6 +89,10 @@ Custom property | Description | Default
         outline: none;
       }
 
+      :host-context([dir="rtl"]) {
+        transform: scaleX(-1);
+      }
+
       #sliderContainer {
         position: relative;
         width: 100%;