[ui/base;css] adding string template expression replacement

ui/webui/resources/css/text_defaults.css

Index: ui/webui/resources/css/text_defaults.css
diff --git a/ui/webui/resources/css/text_defaults.css b/ui/webui/resources/css/text_defaults.css
index 1af823bf961c4fbb298200f3473e848d1c187951..037ade7efb1ba8ba3cf1594976eff8b7f2822e3f 100644
--- a/ui/webui/resources/css/text_defaults.css
+++ b/ui/webui/resources/css/text_defaults.css
@@ -16,14 +16,14 @@
  * Otherwise its $placeholders won't be expanded. */
 
 html {
-  direction: $1;
+  direction: ${textDirection};
 }
 
 body {
-  font-family: $2;
-  font-size: $3;
+  font-family: ${fontFamily};
+  font-size: ${fontSize};
 }
 
 button {
-  font-family: $2;
+  font-family: ${fontFamily};
 }