Use new GN features in the build.

chrome/test/base/js2gtest.gni

 # Copyright 2015 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.
 
 import("//build/module_args/v8.gni")
 
 template("js2gtest") {
   assert(defined(invoker.test_type) &&
          (invoker.test_type == "webui" || invoker.test_type == "unit" ||
           invoker.test_type == "extension"))
@@ skipping 64 matching lines @@
       visibility = [ ":$source_set_name" ]
       sources = invoker.extra_js_files
       outputs = [
         "$root_out_dir/test_data/{{source_root_relative_dir}}/{{source_file_part}}",
       ]
     }
   }
 
   source_set(source_set_name) {
     testonly = true
-    if (defined(invoker.visibility)) {
-      visibility = invoker.visibility
-    }
+    forward_variables_from(invoker,
+                           [
+                             "defines",
+                             "visibility",
+                           ])
     sources = get_target_outputs(":$action_name")
-    if (defined(invoker.defines)) {
-      defines = invoker.defines
-    }
     deps = [
       ":$action_name",
 
       # The generator implicitly makes includes from these targets.
       "//chrome/test:test_support",
       "//testing/gmock",
       "//testing/gtest",
       "//url",
     ]
     if (defined(invoker.deps)) {
       deps += invoker.deps
     }
     if (defined(invoker.extra_js_files)) {
       data_deps = [ ":$copy_target_name" ]
     }
   }
 }