[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 37 matching lines @@
 #       Mojo environment implementation. Defaults to |true| and in general
 #       should only be overridden by mojom targets within the Mojo EDK.
 #
 #   typemaps (optional)
 #       A list of typemap files to apply during bindings generation.
 #
 #   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",
       ]
-      generator_js_outputs = []
-      generator_java_outputs = []
     } else {
       generator_cpp_outputs = [
         "{{source_gen_dir}}/{{source_name_part}}.mojom.cc",
         "{{source_gen_dir}}/{{source_name_part}}.mojom.h",
         "{{source_gen_dir}}/{{source_name_part}}.mojom-internal.h",
       ]
-      generator_js_outputs =
-          [ "{{source_gen_dir}}/{{source_name_part}}.mojom.js" ]
-      generator_java_outputs =
-          [ "{{source_gen_dir}}/{{source_name_part}}.mojom.srcjar" ]
     }
   }
 
+  if (cpp_only) {
+    generator_js_outputs = []
+    generator_java_outputs = []
+  } else {
+    generator_js_outputs =
+        [ "{{source_gen_dir}}/{{source_name_part}}.mojom.js" ]
+    generator_java_outputs =
+        [ "{{source_gen_dir}}/{{source_name_part}}.mojom.srcjar" ]
+  }
+
   if (defined(invoker.sources)) {
     generator_target_name = target_name + "__generator"
     action_foreach(generator_target_name) {
       script = mojom_generator_script
       inputs = mojom_generator_sources
       sources = invoker.sources
       deps = [
         "//mojo/public/tools/bindings:precompile_templates",
       ]
       outputs =
@@ skipping 14 matching lines @@
 
       if (defined(invoker.import_dirs)) {
         foreach(import_dir, invoker.import_dirs) {
           args += [
             "-I",
             rebase_path(import_dir, root_build_dir),
           ]
         }
       }
 
-      if (defined(invoker.variant)) {
+      if (cpp_only) {
         args += [
-          "--variant",
-          invoker.variant,
           "-g",
           "c++",
         ]
       } else {
         args += [
           "-g",
           "c++,javascript,java",
         ]
       }
 
+      if (defined(invoker.variant)) {
+        args += [
+          "--variant",
+          invoker.variant,
+        ]
+      }
+
       if (defined(invoker.typemaps)) {
         foreach(typemap, invoker.typemaps) {
           args += [
             "--typemap",
             rebase_path(typemap, root_build_dir),
           ]
         }
       }
     }
   }
@@ skipping 115 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" ]
     }
   }
 }