Update from chromium https://crrev.com/301315

build/json_to_struct.gypi

+# Copyright 2012 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.
+
+{
+  'variables': {
+    # When including this gypi, the following variables must be set:
+    #   schema_file: a json file that comprise the structure model.
+    #   namespace: the C++ namespace that all generated files go under
+    #   cc_dir: path to generated files
+    # Functions and namespaces can be excluded by setting "nocompile" to true.
+    'struct_gen_dir': '<(DEPTH)/tools/json_to_struct',
+    'struct_gen': '<(struct_gen_dir)/json_to_struct.py',
+  },
+  'rules': [
+    {
+      # GN version: //tools/json_to_struct/json_to_struct.gni
+      'rule_name': 'genstaticinit',
+      'extension': 'json',
+      'inputs': [
+        '<(struct_gen_dir)/element_generator.py',
+        '<(struct_gen_dir)/json_to_struct.py',
+        '<(struct_gen_dir)/struct_generator.py',
+        '<(schema_file)',
+      ],
+      'outputs': [
+        '<(SHARED_INTERMEDIATE_DIR)/<(cc_dir)/<(RULE_INPUT_ROOT).cc',
+        '<(SHARED_INTERMEDIATE_DIR)/<(cc_dir)/<(RULE_INPUT_ROOT).h',
+      ],
+      'action': [
+        'python',
+        '<(struct_gen)',
+        '<(RULE_INPUT_PATH)',
+        '--destbase=<(SHARED_INTERMEDIATE_DIR)',
+        '--destdir=<(cc_dir)',
+        '--namespace=<(namespace)',
+        '--schema=<(schema_file)',
+      ],
+      'message': 'Generating C++ static initializers from <(RULE_INPUT_PATH)',
+      'process_outputs_as_sources': 1,
+    },
+  ],
+  'include_dirs': [
+    '<(SHARED_INTERMEDIATE_DIR)',
+    '<(DEPTH)',
+  ],
+  # This target exports a hard dependency because it generates header
+  # files.
+  'hard_dependency': 1,
+}