[mojo-bindings] Support reuse of native enum classes

mojo/public/tools/bindings/mojom.gni

 # Copyright 2014 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.
 
 mojom_generator_root = "//mojo/public/tools/bindings"
 mojom_generator_script = "$mojom_generator_root/mojom_bindings_generator.py"
 mojom_generator_sources = [
   "$mojom_generator_root/generators/mojom_cpp_generator.py",
   "$mojom_generator_root/generators/mojom_js_generator.py",
   "$mojom_generator_root/generators/mojom_java_generator.py",
@@ skipping 43 matching lines @@
 #   typemaps (optional)
 #       A list of typemap files to apply during bindings generation.
 #
 #   typemap_deps (optional)
 #       A list of public dependencies needed to support active typemaps.
 #
 #   variant (optional)
 #       A variant name to apply to generated bindings. Variant influences
 #       generated source filenames as wells the symbols they define.
 #
+#   cpp_only (optional)
+#       If true, only C++ bindings will be generated. This defaults to false
+#       unless |variant| is specified.
+#
 #   testonly (optional)
 #
 #   visibility (optional)
 template("mojom") {
   assert(
       defined(invoker.sources) || defined(invoker.deps) ||
           defined(invoker.public_deps),
       "\"sources\" or \"deps\" must be defined for the $target_name template.")
 
   cpp_sources_suffix = "cpp_sources"
   cpp_sources_target_name = "${target_name}_${cpp_sources_suffix}"
   cpp_only = false
+  if (defined(invoker.cpp_only)) {
+    cpp_only = invoker.cpp_only
+  }
   if (defined(invoker.sources)) {
     if (defined(invoker.variant)) {
       variant = invoker.variant
       cpp_only = true
       generator_cpp_outputs = [
         "{{source_gen_dir}}/{{source_name_part}}.mojom-${variant}.cc",
         "{{source_gen_dir}}/{{source_name_part}}.mojom-${variant}.h",
         "{{source_gen_dir}}/{{source_name_part}}.mojom-${variant}-internal.h",
       ]
     } else {
@@ skipping 205 matching lines @@
         # //mojo/something:something and we can append "_java" to get the java
         # dependency name.
         full_name = get_label_info(d, "label_no_toolchain")
         deps += [ "${full_name}_java" ]
       }
 
       srcjar_deps = [ ":$java_srcjar_target_name" ]
     }
   }
 }