Convert RuntimeEnabledFeatures.in config file to JSON format.

third_party/WebKit/Source/platform/BUILD.gn

Index: third_party/WebKit/Source/platform/BUILD.gn
diff --git a/third_party/WebKit/Source/platform/BUILD.gn b/third_party/WebKit/Source/platform/BUILD.gn
index 3f266907766e9a6707a87eaea1ae6e126d79b352..57dc61b3ddf0f90a92b1d3c4782bfb574e868c2d 100644
--- a/third_party/WebKit/Source/platform/BUILD.gn
+++ b/third_party/WebKit/Source/platform/BUILD.gn
@@ -98,9 +98,9 @@ action("http_names") {
 action("runtime_enabled_features") {
   script = "../build/scripts/make_runtime_features.py"
 
-  runtime_enabled_features_in = "RuntimeEnabledFeatures.in"
+  runtime_enabled_features_json5 = "RuntimeEnabledFeatures.json5"
   inputs = scripts_for_in_files + [
-             runtime_enabled_features_in,
+             runtime_enabled_features_json5,
              "../build/scripts/templates/RuntimeEnabledFeatures.cpp.tmpl",
              "../build/scripts/templates/RuntimeEnabledFeatures.h.tmpl",
            ]
@@ -111,7 +111,7 @@ action("runtime_enabled_features") {
   ]
 
   args = [
-    rebase_path(runtime_enabled_features_in, root_build_dir),
+    rebase_path(runtime_enabled_features_json5, root_build_dir),
     "--output_dir",
     rebase_path(blink_platform_output_dir, root_build_dir),
   ]