Generate a static struct from fieldtrial_testing_config

tools/variations/fieldtrial_to_struct.gni

-# Copyright 2014 The Chromium Authors. All rights reserved.
+# 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.
 
-# Converts a .json file to a C++ struct.
+# Converts a fieldtrial_testing_config.json file to a C++ struct.
 #
 # Variables:
 #
 #   source (required)
 #       Single file name of source .json file.
 #
 #   schema_file (required)
 #       Single file name of the .json file that defines the schema.
 #
 #   namespace (required)
 #       Namespace name to put result in.
 #
+#   output (required)
+#       Name of the output file.
+#
+#   out_dir (required)
+#       Name of the output directory.
+#
 #   visibility (optional)
 #       Normal meaning.
-template("json_to_struct") {
+template("fieldtrial_to_struct") {
   assert(defined(invoker.source), "source required in $target_name")
   assert(defined(invoker.schema_file), "schema_file required in $target_name")
   assert(defined(invoker.namespace), "namespace required in $target_name")
+  assert(defined(invoker.output), "output required in $target_name")
+  assert(defined(invoker.out_dir), "out_dir required in $target_name")
 
   action_name = target_name + "_action"
   source_set_name = target_name
 
   action(action_name) {
     visibility = [ ":$source_set_name" ]
-    script = "//tools/json_to_struct/json_to_struct.py"
+    script = "//tools/variations/fieldtrial_to_struct.py"
 
     inputs = [
       "//tools/json_to_struct/element_generator.py",
+      "//tools/json_to_struct/json_to_struct.py",
       "//tools/json_to_struct/struct_generator.py",
       invoker.source,
     ]
 
-    out_dir = get_path_info(invoker.source, "gen_dir")
-    out_name = get_path_info(invoker.source, "name")
+    out_dir = get_path_info(invoker.out_dir, "gen_dir")
+    out_name = invoker.output
     outputs = [
       "$out_dir/$out_name.cc",
       "$out_dir/$out_name.h",
     ]
 
     args = [
       rebase_path(invoker.source, root_build_dir),
       "--destbase=" + rebase_path(out_dir, root_build_dir),
       "--namespace=" + invoker.namespace,
       "--schema=" + rebase_path(invoker.schema_file, root_build_dir),
+      "--output=" + invoker.output,
     ]
   }
 
   source_set(source_set_name) {
     if (defined(invoker.visibility)) {
       visibility = invoker.visibility
     }
 
     sources = get_target_outputs(":$action_name")
 
     deps = [
       ":$action_name",
     ]
   }
 }