Update //third_party/protobuf to version 3.

third_party/protobuf/objectivec/GPBUnknownFieldSet_PackagePrivate.h

 // 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
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 // copyright notice, this list of conditions and the following disclaimer
 // in the documentation and/or other materials provided with the
 // distribution.
 //     * Neither the name of Google Inc. nor the names of its
 // contributors may be used to endorse or promote products derived from
 // this software without specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (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: robinson@google.com (Will Robinson)
+#import <Foundation/Foundation.h>
 
+#import "GPBUnknownFieldSet.h"
 
-package google.protobuf.internal;
+@class GPBCodedOutputStream;
+@class GPBCodedInputStream;
 
+@interface GPBUnknownFieldSet ()
 
-message TopLevelMessage {
-  optional ExtendedMessage submessage = 1;
-}
++ (BOOL)isFieldTag:(int32_t)tag;
 
+- (NSData *)data;
 
-message ExtendedMessage {
-  extensions 1 to max;
-}
+- (size_t)serializedSize;
+- (size_t)serializedSizeAsMessageSet;
 
+- (void)writeToCodedOutputStream:(GPBCodedOutputStream *)output;
+- (void)writeAsMessageSetTo:(GPBCodedOutputStream *)output;
 
-message ForeignMessage {
-  optional int32 foreign_message_int = 1;
-}
+- (void)mergeUnknownFields:(GPBUnknownFieldSet *)other;
 
+- (void)mergeFromCodedInputStream:(GPBCodedInputStream *)input;
+- (void)mergeFromData:(NSData *)data;
 
-extend ExtendedMessage {
-  optional int32 optional_int_extension = 1;
-  optional ForeignMessage optional_message_extension = 2;
+- (void)mergeVarintField:(int32_t)number value:(int32_t)value;
+- (BOOL)mergeFieldFrom:(int32_t)tag input:(GPBCodedInputStream *)input;
+- (void)mergeMessageSetMessage:(int32_t)number data:(NSData *)messageData;
 
-  repeated int32 repeated_int_extension = 3;
-  repeated ForeignMessage repeated_message_extension = 4;
-}
+- (void)addUnknownMapEntry:(int32_t)fieldNum value:(NSData *)data;
+
+@end