Move the individual property definitions from client/base/Css to CSSStyleDeclaration.

client/view/SliderMenu.dart

Index: client/view/SliderMenu.dart
diff --git a/client/view/SliderMenu.dart b/client/view/SliderMenu.dart
index c18db2f0dc0eda5dd81524f7799dda6cb51e3df6..19f3eb8f311a96ab76fcb93de06b7ede7e80195d 100644
--- a/client/view/SliderMenu.dart
+++ b/client/view/SliderMenu.dart
@@ -164,7 +164,7 @@ class SliderMenu extends View {
     // triangle) set its width the push the triangle to where we want it.
     String duration = animate ? '.3s' : '0s';
     final triangle = node.query('.sm-triangle');
-    Css.setTransitionDuration(triangle.style, duration);
+    triangle.style.transitionDuration = duration;
     FxUtil.setWebkitTransform(triangle, x, 0);
   }
 }