Fix protobuf's Python runtime and imports.

third_party/dom_distiller_js/BUILD.gn

Index: third_party/dom_distiller_js/BUILD.gn
diff --git a/third_party/dom_distiller_js/BUILD.gn b/third_party/dom_distiller_js/BUILD.gn
index ddd14d982132092d1c035384defed1406ed2b914..6af4edc8c5002fef632b24887284c39938654da0 100644
--- a/third_party/dom_distiller_js/BUILD.gn
+++ b/third_party/dom_distiller_js/BUILD.gn
@@ -39,6 +39,10 @@ proto_library("dom_distiller_proto") {
   generator_plugin_script_deps = protoc_plugin_files
   generator_plugin_suffixes = [ "_json_converter.h" ]
   generator_plugin_options = "output_dir=:"
+
+  deps = [
+    "//third_party/protobuf:py_proto",
+  ]
 }
 
 # The purpose of json_values_converter_test_proto is to test the
@@ -54,6 +58,10 @@ proto_library("json_values_converter_test_proto") {
   generator_plugin_script_deps = protoc_plugin_files
   generator_plugin_suffixes = [ "_json_converter.h" ]
   generator_plugin_options = "output_dir=:"
+
+  deps = [
+    "//third_party/protobuf:py_proto",
+  ]
 }
 
 action("json_values_converter_tests") {