Fix protobuf's Python runtime and imports.

third_party/dom_distiller_js/protoc_plugins/util/plugin_protos.py

Index: third_party/dom_distiller_js/protoc_plugins/util/plugin_protos.py
diff --git a/third_party/dom_distiller_js/protoc_plugins/util/plugin_protos.py b/third_party/dom_distiller_js/protoc_plugins/util/plugin_protos.py
index 009987dfd18b1a5d0357847a45ca308b4b381be4..e60cba19618783049cb7d6d15956021f5dddfb32 100644
--- a/third_party/dom_distiller_js/protoc_plugins/util/plugin_protos.py
+++ b/third_party/dom_distiller_js/protoc_plugins/util/plugin_protos.py
@@ -12,22 +12,22 @@ and https://developers.google.com/protocol-buffers/docs/reference/cpp/google.pro
 import os
 import sys
 
-SCRIPT_DIR = os.path.dirname(__file__)
-SRC_DIR = os.path.abspath(os.path.join(SCRIPT_DIR, '..', '..', '..', '..'))
-
-sys.path.insert(
-    1, os.path.join(SRC_DIR, 'third_party', 'protobuf', 'python'))
-sys.path.insert(
-    1, os.path.join(SRC_DIR, 'third_party', 'protobuf', 'third_party', 'six'))
+PYPROTO_DIR = os.path.abspath('pyproto')
+sys.path.insert(0, PYPROTO_DIR)
+import google.protobuf
+
+FOO = os.path.abspath( \
+  os.path.join(os.path.dirname(google.protobuf.__file__), '..', '..'))
+if PYPROTO_DIR != FOO:
+  print >> sys.stderr, 'PYPROTO_DIR = ' + PYPROTO_DIR
+  print >> sys.stderr, 'FOO = ' + FOO
+  assert False
+
+from google.protobuf.compiler import plugin_pb2
 from google.protobuf.descriptor_pb2 import FieldDescriptorProto
 
 from . import types
 
-sys.path.insert(
-    1, os.path.join(SRC_DIR,
-                    'third_party', 'dom_distiller_js', 'dist', 'python'))
-import plugin_pb2
-
 
 class PluginRequest(object):
   def __init__(self, proto):