Reverts third_party/protobuf: Update to HEAD (f52e188fe4)

third_party/protobuf/src/google/protobuf/util/internal/testdata/books.proto

 // 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.
@@ skipping 13 matching lines @@
 // 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: sven@google.com (Sven Mawson)
 //
 // Sample protos for testing.
-
-// Some of the older enums don't use CAPITALS_WITH_UNDERSCORES for testing.
-// LINT: LEGACY_NAMES
-
 syntax = "proto2";
 
 package google.protobuf.testing;
 
 // A book
 message Book {
   optional string title = 1;
   optional Author author = 2;
   optional uint32 length = 3;
   optional int64 published = 4;
   optional bytes content = 5;
 
   optional group Data = 6 {
     optional uint32 year = 7;
     optional string copyright = 8;
   }
 
   message Label {
     optional string key = 1;
     optional string value = 2;
   }
 
   optional Publisher publisher = 9;
   repeated Label labels = 10;
 
   enum Type {
     FICTION = 1;
     KIDS = 2;
     ACTION_AND_ADVENTURE = 3;
-    arts_and_photography = 4;
   }
   optional Type type = 11;
 
   extensions 200 to 499;
 }
 
 // A publisher of a book, tests required fields.
 message Publisher {
   required string name = 1;
 }
@@ skipping 105 matching lines @@
 }
 
 // A recursively defined message.
 message Cyclic {
   optional int32 m_int = 1;
   optional string m_str = 2;
   optional Book m_book = 3;
   repeated Author m_author = 5;
   optional Cyclic m_cyclic = 4;
 }