Revert https://codereview.chromium.org/1291903002 (protobuf roll).

third_party/protobuf/objectivec/GPBUnknownFieldSet_PackagePrivate.h

-// Protocol Buffers - Google's data interchange format
-// Copyright 2008 Google Inc.  All rights reserved.
-// 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.
-
-#import <Foundation/Foundation.h>
-
-#import "GPBUnknownFieldSet.h"
-
-@class GPBCodedOutputStream;
-@class GPBCodedInputStream;
-
-@interface GPBUnknownFieldSet ()
-
-+ (BOOL)isFieldTag:(int32_t)tag;
-
-- (NSData *)data;
-
-- (size_t)serializedSize;
-- (size_t)serializedSizeAsMessageSet;
-
-- (void)writeToCodedOutputStream:(GPBCodedOutputStream *)output;
-- (void)writeAsMessageSetTo:(GPBCodedOutputStream *)output;
-
-- (void)mergeUnknownFields:(GPBUnknownFieldSet *)other;
-
-- (void)mergeFromCodedInputStream:(GPBCodedInputStream *)input;
-- (void)mergeFromData:(NSData *)data;
-
-- (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;
-
-- (void)addUnknownMapEntry:(int32_t)fieldNum value:(NSData *)data;
-
-@end