Update //third_party/protobuf to version 3.

third_party/protobuf/java/src/test/java/com/google/protobuf/test_custom_options.proto

Index: third_party/protobuf/java/src/test/java/com/google/protobuf/test_custom_options.proto
diff --git a/third_party/protobuf/src/google/protobuf/unittest_lite_imports_nonlite.proto b/third_party/protobuf/java/src/test/java/com/google/protobuf/test_custom_options.proto
similarity index 81%
copy from third_party/protobuf/src/google/protobuf/unittest_lite_imports_nonlite.proto
copy to third_party/protobuf/java/src/test/java/com/google/protobuf/test_custom_options.proto
index d52cb8cc36d8924a3454f9170f6b338f14a59c5c..f8efd455a1eb2b6fcde9927d5fd4f3724434b84a 100644
--- a/third_party/protobuf/src/google/protobuf/unittest_lite_imports_nonlite.proto
+++ b/third_party/protobuf/java/src/test/java/com/google/protobuf/test_custom_options.proto
@@ -1,6 +1,6 @@
 // Protocol Buffers - Google's data interchange format
 // Copyright 2008 Google Inc.  All rights reserved.
-// http://code.google.com/p/protobuf/
+// https://developers.google.com/protocol-buffers/
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
@@ -28,16 +28,17 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-// Author: kenton@google.com (Kenton Varda)
+// Author: Feng Xiao (xiaofeng@google.com)
 //
-// Tests that a "lite" message can import a regular message.
+// Test that custom options defined in a proto file's dependencies are properly
+// initialized.
+syntax = "proto2";
 
 package protobuf_unittest;
 
-import "google/protobuf/unittest.proto";
 
-option optimize_for = LITE_RUNTIME;
+import "google/protobuf/unittest_custom_options.proto";
 
-message TestLiteImportsNonlite {
-  optional TestAllTypes message = 1;
+message TestMessageWithCustomOptionsContainer {
+  optional TestMessageWithCustomOptions field = 1;
 }