Update //third_party/protobuf to version 3.

third_party/protobuf/objectivec/GPBUnknownField.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: kenton@google.com (Kenton Varda)
-//  Based on original Protocol Buffers design by
-//  Sanjay Ghemawat, Jeff Dean, and others.
-//
-// A proto file which is imported by unittest.proto to test importing.
+#import <Foundation/Foundation.h>
 
+@class GPBCodedOutputStream;
+@class GPBUInt32Array;
+@class GPBUInt64Array;
+@class GPBUnknownFieldSet;
 
-// We don't put this in a package within proto2 because we need to make sure
-// that the generated code doesn't depend on being in the proto2 namespace.
-// In test_util.h we do
-// "using namespace unittest_import = protobuf_unittest_import".
-package protobuf_unittest_import;
+NS_ASSUME_NONNULL_BEGIN
 
-option optimize_for = SPEED;
+@interface GPBUnknownField : NSObject<NSCopying>
 
-// Excercise the java_package option.
-option java_package = "com.google.protobuf.test";
+@property(nonatomic, readonly, assign) int32_t number;
 
-// Do not set a java_outer_classname here to verify that Proto2 works without
-// one.
+// Only one of these will be set.
+@property(nonatomic, readonly, strong) GPBUInt64Array *varintList;
+@property(nonatomic, readonly, strong) GPBUInt32Array *fixed32List;
+@property(nonatomic, readonly, strong) GPBUInt64Array *fixed64List;
+@property(nonatomic, readonly, strong) NSArray *lengthDelimitedList;  // NSData
+@property(nonatomic, readonly, strong) NSArray *groupList;  // GPBUnknownFieldSet
 
-// Test public import
-import public "google/protobuf/unittest_import_public.proto";
+// Only one of these should be used per Field.
+- (void)addVarint:(uint64_t)value;
+- (void)addFixed32:(uint32_t)value;
+- (void)addFixed64:(uint64_t)value;
+- (void)addLengthDelimited:(NSData *)value;
+- (void)addGroup:(GPBUnknownFieldSet *)value;
 
-message ImportMessage {
-  optional int32 d = 1;
-}
+@end
 
-enum ImportEnum {
-  IMPORT_FOO = 7;
-  IMPORT_BAR = 8;
-  IMPORT_BAZ = 9;
-}
-
+NS_ASSUME_NONNULL_END