[Extensions] Add extension feature generation code

tools/json_schema_compiler/test/BUILD.gn

Index: tools/json_schema_compiler/test/BUILD.gn
diff --git a/tools/json_schema_compiler/test/BUILD.gn b/tools/json_schema_compiler/test/BUILD.gn
index 22a23af979ad9c3063e5b3274976e4c8c8e49245..e6d9cc0da812453cdc257982f70012c18cae8579 100644
--- a/tools/json_schema_compiler/test/BUILD.gn
+++ b/tools/json_schema_compiler/test/BUILD.gn
@@ -2,7 +2,9 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/config/features.gni")
 import("//build/json_schema_api.gni")
+import("//tools/json_schema_compiler/json_features.gni")
 
 json_schema_api("api") {
   visibility = [ ":*" ]
@@ -32,7 +34,18 @@ json_schema_api("api") {
   root_namespace = "test::api::%(namespace)s"
 }
 
-source_set("test") {
+if (enable_extensions) {
+  json_features("features_test") {
+    feature_class = "APIFeature"
+    provider_class = "TestAPIFeatureProvider"
+    sources = [
+      "features_test.json",
+      "features_test2.json",
+    ]
+  }
+}
+
+source_set("schema_test") {
   testonly = true
   sources = [
     "test_util.cc",
@@ -47,3 +60,12 @@ source_set("test") {
     "//base",
   ]
 }
+
+if (enable_extensions) {
+  source_set("features_generation_test") {
+    testonly = true
+    public_deps = [
+      ":features_test",
+    ]
+  }
+}