gn: start of format command

tools/gn/gn.gyp

 {
   'variables': {
     'chromium_code': 1,
   },
   'targets': [
     {
       'target_name': 'gn_lib',
       'type': 'static_library',
       'dependencies': [
         '../../base/base.gyp:base',
@@ skipping 12 matching lines @@
         'builder.cc',
         'builder.h',
         'builder_record.cc',
         'builder_record.h',
         'c_include_iterator.cc',
         'c_include_iterator.h',
         'command_args.cc',
         'command_check.cc',
         'command_desc.cc',
         'command_gen.cc',
+        'command_format.cc',
         'command_help.cc',
         'command_ls.cc',
         'command_refs.cc',
         'commands.cc',
         'commands.h',
         'config.cc',
         'config.h',
         'config_values.cc',
         'config_values.h',
         'config_values_extractors.cc',
@@ skipping 146 matching lines @@
         '../../base/third_party/dynamic_annotations/dynamic_annotations.gyp:dynamic_annotations',
       ],
     },
     {
       'target_name': 'gn_unittests',
       'type': '<(gtest_target_type)',
       'sources': [
         'action_target_generator_unittest.cc',
         'builder_unittest.cc',
         'c_include_iterator_unittest.cc',
+        'command_format_unittest.cc',
         'config_values_extractors_unittest.cc',
         'escape_unittest.cc',
         'filesystem_utils_unittest.cc',
         'function_foreach_unittest.cc',
         'function_get_label_info_unittest.cc',
         'function_get_path_info_unittest.cc',
         'function_get_target_outputs_unittest.cc',
         'function_process_file_template_unittest.cc',
         'function_rebase_path_unittest.cc',
         'function_write_file_unittest.cc',
@@ skipping 42 matching lines @@
       'type': 'executable',
       'sources': [
         'generate_test_gn_data.cc',
       ],
       'dependencies': [
         '../../base/base.gyp:base',
       ],
     }
   ],
 }