Update //third_party/protobuf to version 3.

third_party/protobuf/objectivec/generate_descriptors_proto.sh

+#!/bin/bash
+
+# Run this script to regenerate descriptor.pbobjc.{h,m} after the protocol
+# compiler changes.
+
+# HINT:  Flags passed to generate_descriptor_proto.sh will be passed directly
+#   to make when building protoc.  This is particularly useful for passing
+#   -j4 to run 4 jobs simultaneously.
+
+set -eu
+
+readonly ScriptDir=$(dirname "$(echo $0 | sed -e "s,^\([^/]\),$(pwd)/\1,")")
+readonly ProtoRootDir="${ScriptDir}/.."
+
+pushd "${ProtoRootDir}" > /dev/null
+
+if test ! -e src/google/protobuf/stubs/common.h; then
+  cat >&2 << __EOF__
+Could not find source code.  Make sure you are running this script from the
+root of the distribution tree.
+__EOF__
+  exit 1
+fi
+
+if test ! -e src/Makefile; then
+  cat >&2 << __EOF__
+Could not find src/Makefile.  You must run ./configure (and perhaps
+./autogen.sh) first.
+__EOF__
+  exit 1
+fi
+
+# Make sure the compiler is current.
+cd src
+make $@ protoc
+
+declare -a RUNTIME_PROTO_FILES=( \
+  google/protobuf/any.proto \
+  google/protobuf/api.proto \
+  google/protobuf/descriptor.proto \
+  google/protobuf/duration.proto \
+  google/protobuf/empty.proto \
+  google/protobuf/field_mask.proto \
+  google/protobuf/source_context.proto \
+  google/protobuf/struct.proto \
+  google/protobuf/timestamp.proto \
+  google/protobuf/type.proto \
+  google/protobuf/wrappers.proto)
+
+./protoc --objc_out="${ProtoRootDir}/objectivec" ${RUNTIME_PROTO_FILES[@]}