Generate the proto JSON converter for DOM distiller

third_party/protobuf/proto_library.gni

Index: third_party/protobuf/proto_library.gni
diff --git a/third_party/protobuf/proto_library.gni b/third_party/protobuf/proto_library.gni
index 050154ce8cfbd559e01f24346ca22f7da88af1f5..f133de86012c1ceddac8167678ab6fd9beea51b0 100644
--- a/third_party/protobuf/proto_library.gni
+++ b/third_party/protobuf/proto_library.gni
@@ -41,6 +41,9 @@
 #   generator_plugin_options (optional)
 #       Extra flags passed to the plugin. See cc_generator_options.
 #
+#   json_converter (optional)
+#       The plugin executable to generate JSON converter.
+#
 #   cc_include (optional)
 #       String listing an extra include that should be passed.
 #       Example: cc_include = "foo/bar.h"
@@ -48,6 +51,9 @@
 #   deps (optional)
 #       Additional dependencies.
 #
+#   inputs (optional)
+#       Additional inputs for dependency checking.
+#
 # Parameters for compiling the generated code:
 #
 #   component_build_force_source_set (Default=false)
@@ -103,6 +109,11 @@ template("proto_library") {
 
     outputs = []
 
+    inputs = []
+    if (defined(invoker.inputs)) {
+      inputs += invoker.inputs
+    }
+
     args = []
     if (defined(invoker.cc_include)) {
       args += [
@@ -209,11 +220,19 @@ template("proto_library") {
     if (defined(invoker.deps)) {
       deps += invoker.deps
     }
+
+    if (defined(invoker.json_converter)) {
+      args += [
+        "--plugin=protoc-gen-json_converter=" +
+            rebase_path(invoker.json_converter, root_build_dir),
+        "--json_converter_out=output_dir=:$rel_out_dir",
+      ]
+      outputs += [ "$out_dir/{{source_name_part}}_json_converter.h" ]
+    }
   }
 
   if (defined(invoker.component_build_force_source_set) &&
-      invoker.component_build_force_source_set &&
-      is_component_build) {
+      invoker.component_build_force_source_set && is_component_build) {
     link_target_type = "source_set"
   } else {
     link_target_type = "static_library"