mojom: Allow mojoms to only run a subset of the bindings generators.

mojo/public/tools/bindings/mojom_bindings_generator.gypi

 # Copyright 2013 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.
 
 {
   'rules': [
     {
       'rule_name': '<(_target_name)_mojom_bindings_generator',
       'extension': 'mojom',
       'variables': {
         'mojom_base_output_dir':
              '<!(python <(DEPTH)/build/inverse_depth.py <(DEPTH))',
         'mojom_bindings_generator':
             '<(DEPTH)/mojo/public/tools/bindings/mojom_bindings_generator.py',
         'java_out_dir': '<(PRODUCT_DIR)/java_mojo/<(_target_name)/src',
         'mojom_import_args%': [
          '-I<(DEPTH)'
         ],
+        'mojom_additional_args%': [
+        ],
       },
       'inputs': [
         '<(mojom_bindings_generator)',
         '<(DEPTH)/mojo/public/tools/bindings/generators/cpp_templates/enum_declaration.tmpl',
         '<(DEPTH)/mojo/public/tools/bindings/generators/cpp_templates/interface_declaration.tmpl',
         '<(DEPTH)/mojo/public/tools/bindings/generators/cpp_templates/interface_definition.tmpl',
         '<(DEPTH)/mojo/public/tools/bindings/generators/cpp_templates/interface_macros.tmpl',
         '<(DEPTH)/mojo/public/tools/bindings/generators/cpp_templates/interface_proxy_declaration.tmpl',
         '<(DEPTH)/mojo/public/tools/bindings/generators/cpp_templates/interface_request_validator_declaration.tmpl',
         '<(DEPTH)/mojo/public/tools/bindings/generators/cpp_templates/interface_response_validator_declaration.tmpl',
@@ skipping 49 matching lines @@
         '<(SHARED_INTERMEDIATE_DIR)/<(mojom_base_output_dir)/<(RULE_INPUT_DIRNAME)/<(RULE_INPUT_ROOT).mojom.js',
         '<(SHARED_INTERMEDIATE_DIR)/<(mojom_base_output_dir)/<(RULE_INPUT_DIRNAME)/<(RULE_INPUT_ROOT)_mojom.py',
         '<(SHARED_INTERMEDIATE_DIR)/<(mojom_base_output_dir)/<(RULE_INPUT_DIRNAME)/<(RULE_INPUT_ROOT).mojom-internal.h',
       ],
       'action': [
         'python', '<@(mojom_bindings_generator)',
         './<(RULE_INPUT_DIRNAME)/<(RULE_INPUT_ROOT).mojom',
         '--use_chromium_bundled_pylibs',
         '-d', '<(DEPTH)',
         '<@(mojom_import_args)',
+        '<@(mojom_additional_args)',
         '-o', '<(SHARED_INTERMEDIATE_DIR)/<(mojom_base_output_dir)/<(RULE_INPUT_DIRNAME)',
         '--java_output_directory=<(java_out_dir)',
       ],
       'message': 'Generating Mojo bindings from <(RULE_INPUT_DIRNAME)/<(RULE_INPUT_ROOT).mojom',
       'process_outputs_as_sources': 1,
     }
   ],
   'include_dirs': [
     '<(DEPTH)',
     '<(SHARED_INTERMEDIATE_DIR)',
   ],
   'direct_dependent_settings': {
     'include_dirs': [
       '<(DEPTH)',
       '<(SHARED_INTERMEDIATE_DIR)',
     ],
     'variables': {
       'generated_src_dirs': [
         '<(PRODUCT_DIR)/java_mojo/<(_target_name)/src',
       ],
     },
   },
   'hard_dependency': 1,
 }