Convert RuntimeEnabledFeatures.in config file to JSON format.

components/test_runner/test_interfaces.cc

Index: components/test_runner/test_interfaces.cc
diff --git a/components/test_runner/test_interfaces.cc b/components/test_runner/test_interfaces.cc
index 994ae7a7085896b26466b0d7594e1b9dc54ce02c..4258c3fee47b42432d6987a3cffbe53664bb35cb 100644
--- a/components/test_runner/test_interfaces.cc
+++ b/components/test_runner/test_interfaces.cc
@@ -31,7 +31,7 @@ TestInterfaces::TestInterfaces()
       main_view_(nullptr) {
   blink::setLayoutTestMode(true);
   // NOTE: please don't put feature specific enable flags here,
-  // instead add them to RuntimeEnabledFeatures.in
+  // instead add them to RuntimeEnabledFeatures.json5
 
   ResetAll();
 }