Enable Roboto by default for testing purpose.

ui/base/font_helper_chromeos.h

Index: ui/base/font_helper_chromeos.h
diff --git a/ui/base/font_helper_chromeos.h b/ui/base/font_helper_chromeos.h
index ca3508c7fa145eec51f8280dba5968ef4fc5e3c2..e2013ce2e23bcb4c68f4d38a514807c423556ae9 100644
--- a/ui/base/font_helper_chromeos.h
+++ b/ui/base/font_helper_chromeos.h
@@ -11,11 +11,11 @@ namespace ui {
 
 // This is a temporary helper function for the Roboto UI font experiment.
 // It'll go away once the experiment is over.
-// See http://crbug.com/434400 for more details.
+// See http://crbug.com/434400 and http://crbug.com/448948 for more details.
 //
-// "Noto Sans UI" is the primary UI font (both native and web) in most
-// locales and we're replacing it with 'Roboto' when 'enable-roboto-font-ui'
-// flag is on.
+// "Noto Sans UI" was the primary UI font (both native and web) in most
+// locales and we're replacing it with 'Roboto'. For now 'Roboto' is enabled by
+// default and can be disabled by setting 'disable-roboto-font-ui' flag to on.
 void ReplaceNotoSansWithRobotoIfEnabled(std::string* font_family);
 
 }  // namespace ui