Fix protobuf's Python runtime and imports.

tools/protoc_wrapper/protoc_wrapper.py

 #!/usr/bin/env python
 # Copyright (c) 2012 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.
 
 """
 A simple wrapper for protoc.
 Script for //third_party/protobuf/proto_library.gni .
 Features:
 - Inserts #include for extra header automatically.
@@ skipping 49 matching lines @@
 
       if not include_point_found:
         raise RuntimeError("Include point not found in header: "
                            "{0} .".format(filename))
 
     with open(filename, "w") as f:
       for line in contents:
         print(line, file=f)
 
 
+def WritePythonInit(base_dir, protos):
+  def write_init_py(path):
+    if not path:
+      return
+    open(os.path.join(base_dir, path, '__init__.py'), 'a').close()
+    write_init_py(os.path.dirname(path))
+
+  for proto in protos:
+    write_init_py(os.path.dirname(proto))
+
+
 def main(argv):
   parser = argparse.ArgumentParser()
   parser.add_argument("--protoc",
                       help="Relative path to compiler.")
 
   parser.add_argument("--proto-in-dir",
                       help="Base directory with source protos.")
   parser.add_argument("--cc-out-dir",
                       help="Output directory for standard C++ generator.")
   parser.add_argument("--py-out-dir",
@@ skipping 49 matching lines @@
   protoc_cmd += [os.path.join(proto_dir, name) for name in protos]
 
   ret = subprocess.call(protoc_cmd)
   if ret != 0:
     raise RuntimeError("Protoc has returned non-zero status: "
                        "{0} .".format(ret))
 
   if options.include:
     WriteIncludes(headers, options.include)
 
+  if options.py_out_dir:
+    WritePythonInit(options.py_out_dir, protos)
+
 
 if __name__ == "__main__":
   try:
     main(sys.argv)
   except RuntimeError as e:
     print(e, file=sys.stderr)
     sys.exit(1)