Add support for Java nano protocol buffers for Android.

build/protoc_java.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.
 
-"""Generate java source files from protobufs
+"""Generate java source files from protobuf files.
 
 Usage:
-    protoc_java.py {protoc} {proto_path} {java_out} {stamp_file} {proto_files}
+    protoc_java.py {protoc} {proto_path} {java_out} {proto_runtime} \
+        {stamp_file} {proto_files}
 
 This is a helper file for the genproto_java action in protoc_java.gypi.
 
 It performs the following steps:
 1. Deletes all old sources (ensures deleted classes are not part of new jars).
 2. Creates source directory.
 3. Generates Java files using protoc.
 4. Creates a new stamp file.
+
+proto_runtime must be one of 'nano' and 'lite'.
 """
 
 import os
 import shutil
 import subprocess
 import sys
 
 def main(argv):
-  if len(argv) < 5:
+  if len(argv) < 6:
     usage()
     return 1
 
-  protoc_path, proto_path, java_out, stamp_file = argv[1:5]
-  proto_files = argv[5:]
+  protoc_path, proto_path, java_out, proto_runtime, stamp_file = argv[1:6]
+  proto_files = argv[6:]
 
-  # Delete all old sources
+  # Delete all old sources.
   if os.path.exists(java_out):
     shutil.rmtree(java_out)
 
-  # Create source directory
+  # Create source directory.
   os.makedirs(java_out)
 
-  # Generate Java files using protoc
+  # Figure out which runtime to use.
+  if proto_runtime == 'nano':
+    out_arg = '--javanano_out=optional_field_style=reftypes,' + \
+        'store_unknown_fields=true:' + java_out
+  elif proto_runtime == 'lite':
+    out_arg = '--java_out=' + java_out
+  else:
+    usage()
+    return 1
+
+  # Generate Java files using protoc.
   ret = subprocess.call(
-      [protoc_path, '--proto_path', proto_path, '--java_out', java_out]
-      + proto_files)
+      [protoc_path, '--proto_path', proto_path, out_arg] + proto_files)
 
   if ret == 0:
-    # Create a new stamp file
+    # Create a new stamp file.
     with file(stamp_file, 'a'):
       os.utime(stamp_file, None)
 
   return ret
 
 def usage():
   print(__doc__);
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv))