Add more components_unittests to GN build

components/json_schema/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-static_library("json_schema") {
+source_set("json_schema") {
   sources = [
     "json_schema_constants.cc",
     "json_schema_constants.h",
     "json_schema_validator.cc",
     "json_schema_validator.h",
   ]
 
   deps = [
     "//base",
     "//third_party/re2",
   ]
 }
+
+source_set("unit_tests") {
+  testonly = true
+  sources = [
+    "json_schema_validator_unittest.cc",
+    "json_schema_validator_unittest_base.cc",
+    "json_schema_validator_unittest_base.h",
+  ]
+  deps = [
+    ":json_schema",
+    "//testing/gtest",
+  ]
+}