Revert "third_party/protobuf: Update to HEAD (83d681ee2c)"

third_party/protobuf/src/google/protobuf/duration.proto

Index: third_party/protobuf/src/google/protobuf/duration.proto
diff --git a/third_party/protobuf/src/google/protobuf/duration.proto b/third_party/protobuf/src/google/protobuf/duration.proto
index 7f461f408d82f602ff9f106df2caf2d8c1a86848..96c1796d6594a63f05a8beb18d895633b5529ae4 100644
--- a/third_party/protobuf/src/google/protobuf/duration.proto
+++ b/third_party/protobuf/src/google/protobuf/duration.proto
@@ -33,11 +33,11 @@ syntax = "proto3";
 package google.protobuf;
 
 option csharp_namespace = "Google.Protobuf.WellKnownTypes";
-option cc_enable_arenas = true;
 option go_package = "github.com/golang/protobuf/ptypes/duration";
 option java_package = "com.google.protobuf";
 option java_outer_classname = "DurationProto";
 option java_multiple_files = true;
+option java_generate_equals_and_hash = true;
 option objc_class_prefix = "GPB";
 
 // A Duration represents a signed, fixed-length span of time represented
@@ -81,12 +81,6 @@ option objc_class_prefix = "GPB";
 //       end.nanos -= 1000000000;
 //     }
 //
-// Example 3: Compute Duration from datetime.timedelta in Python.
-//
-//     td = datetime.timedelta(days=3, minutes=10)
-//     duration = Duration()
-//     duration.FromTimedelta(td)
-//
 //
 message Duration {