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

third_party/protobuf/examples/addressbook.proto

-// See README.txt for information and build instructions.
-
-syntax = "proto3";
-
-package tutorial;
-
-option java_package = "com.example.tutorial";
-option java_outer_classname = "AddressBookProtos";
-option csharp_namespace = "Google.Protobuf.Examples.AddressBook";
-
-message Person {
-  string name = 1;
-  int32 id = 2;        // Unique ID number for this person.
-  string email = 3;
-
-  enum PhoneType {
-    MOBILE = 0;
-    HOME = 1;
-    WORK = 2;
-  }
-
-  message PhoneNumber {
-    string number = 1;
-    PhoneType type = 2;
-  }
-
-  repeated PhoneNumber phones = 4;
-}
-
-// Our address book file is just one of these.
-message AddressBook {
-  repeated Person people = 1;
-}