Update //third_party/protobuf to version 3.

third_party/protobuf/protobuf_nacl.gyp

 # Copyright 2014 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.
 
 {
   'includes': [
     '../../native_client/build/untrusted.gypi',
   ],
   'targets': [
     {
       'target_name': 'protobuf_lite_nacl',
       'type': 'none',
       'variables': {
         'nlib_target': 'libprotobuf_lite_nacl.a',
         'build_glibc': 0,
         'build_newlib': 0,
         'build_pnacl_newlib': 1,
-        'config_h_dir': '.',
       },
       'pnacl_compile_flags': [

[Peter Kasting, 2016/04/06 22:35:39]

You should be able to remove this block, I think.

[xyzzyz, 2016/04/07 18:55:02]

Done.

         # This disables #warning in hash_map/hash_set headers which are
         # deprecated but still used in protobuf.
         #
         # TODO(sergeyu): Migrate protobuf to unordered_man and unordered_set
         # and remove this flag.
         '-Wno-#warnings',
       ],
       'includes': [
         'protobuf_lite.gypi',
       ],
+      'defines': [
+        # protobuf requires these to be set manually, as it no longer
+        # uses config.h
+        'HAVE_ZLIB',

[Peter Kasting, 2016/04/06 22:35:39]

Do you really need this?

[xyzzyz, 2016/04/07 18:55:02]

Seems like I actually don't. Thanks!

+        'HAVE_PTHREAD',

[Peter Kasting, 2016/04/06 22:35:39]

In my roll attempt I set this in protobuf_lite.gypi instead.  Why doesn't it
need to be set there (in which case you don't need the one here)?

[xyzzyz, 2016/04/07 18:55:02]

I set it in protobuf.gyp, and it seems you're right that I don't need to set it
here. Do you think it would be better to set it in protobuf_lite.gyp?

[Peter Kasting, 2016/04/07 23:25:38]

If it affects files listed in protobuf_lit.gypi, then it should be set in
protobuf_lite.gypi.  Otherwise if someone creates a new .gyp that includes that
.gypi, they won't get the #define, and things will be a mess.

[xyzzyz, 2016/04/11 19:34:40]

Done.

+      ],
     },  # end of target 'protobuf_lite_nacl'
   ]
 }