Convert RuntimeEnabledFeatures.in config file to JSON format.

third_party/WebKit/Source/core/BUILD.gn

Index: third_party/WebKit/Source/core/BUILD.gn
diff --git a/third_party/WebKit/Source/core/BUILD.gn b/third_party/WebKit/Source/core/BUILD.gn
index 19c6a9ebc71a8003a2e222214ae679903d909678..018d9ed6f4c112077c57b9294980caf55058dde1 100644
--- a/third_party/WebKit/Source/core/BUILD.gn
+++ b/third_party/WebKit/Source/core/BUILD.gn
@@ -381,7 +381,7 @@ action("generated_testing_idls_internal_runtime_flags") {
 
   inputs = scripts_for_in_files + [
              "../build/scripts/make_internal_runtime_flags.py",
-             "../platform/RuntimeEnabledFeatures.in",
+             "../platform/RuntimeEnabledFeatures.json5",
              "../build/scripts/templates/InternalRuntimeFlags.h.tmpl",
              "../build/scripts/templates/InternalRuntimeFlags.idl.tmpl",
            ]
@@ -391,7 +391,7 @@ action("generated_testing_idls_internal_runtime_flags") {
   ]
 
   args = [
-    rebase_path("../platform/RuntimeEnabledFeatures.in", root_build_dir),
+    rebase_path("../platform/RuntimeEnabledFeatures.json5", root_build_dir),
     "--output_dir",
     "$rel_blink_core_gen_dir/testing",
   ]
@@ -804,7 +804,7 @@ action("make_core_generated_origin_trials") {
 
   inputs = scripts_for_in_files + [
              "../build/scripts/make_origin_trials.py",
-             "../platform/RuntimeEnabledFeatures.in",
+             "../platform/RuntimeEnabledFeatures.json5",
              "../build/scripts/templates/OriginTrials.cpp.tmpl",
              "../build/scripts/templates/OriginTrials.h.tmpl",
            ]
@@ -814,7 +814,7 @@ action("make_core_generated_origin_trials") {
   ]
 
   args = [
-    rebase_path("../platform/RuntimeEnabledFeatures.in", root_build_dir),
+    rebase_path("../platform/RuntimeEnabledFeatures.json5", root_build_dir),
     "--output_dir",
     "$rel_blink_core_gen_dir/origin_trials",
   ]