Update //third_party/protobuf to version 3.

third_party/protobuf/objectivec/GPBUnknownFieldSet.h

Index: third_party/protobuf/objectivec/GPBUnknownFieldSet.h
diff --git a/third_party/protobuf/src/google/protobuf/io/zero_copy_stream.cc b/third_party/protobuf/objectivec/GPBUnknownFieldSet.h
similarity index 77%
copy from third_party/protobuf/src/google/protobuf/io/zero_copy_stream.cc
copy to third_party/protobuf/objectivec/GPBUnknownFieldSet.h
index dad6ff14468d031f16baafb2f1ca567961251c43..d785ca16e74cb68f5d5a842b1bdcef94dd8ca15d 100644
--- a/third_party/protobuf/src/google/protobuf/io/zero_copy_stream.cc
+++ b/third_party/protobuf/objectivec/GPBUnknownFieldSet.h
@@ -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
@@ -28,21 +28,23 @@
 // (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)
-//  Based on original Protocol Buffers design by
-//  Sanjay Ghemawat, Jeff Dean, and others.
+#import <Foundation/Foundation.h>
 
-#include <google/protobuf/io/zero_copy_stream.h>
+@class GPBUnknownField;
 
+NS_ASSUME_NONNULL_BEGIN
 
-namespace google {
-namespace protobuf {
-namespace io {
+@interface GPBUnknownFieldSet : NSObject<NSCopying>
 
-ZeroCopyInputStream::~ZeroCopyInputStream() {}
-ZeroCopyOutputStream::~ZeroCopyOutputStream() {}
+- (BOOL)hasField:(int32_t)number;
+- (nullable GPBUnknownField *)getField:(int32_t)number;
+- (NSUInteger)countOfFields;
 
+- (void)addField:(GPBUnknownField *)field;
 
-}  // namespace io
-}  // namespace protobuf
-}  // namespace google
+// Returns an NSArray of the GPBFields sorted by the field numbers.
+- (NSArray *)sortedFields;
+
+@end
+
+NS_ASSUME_NONNULL_END