Update third_party/protobuf to protobuf-v3.0.0-beta-3

third_party/protobuf/src/google/protobuf/field_mask.proto

Index: third_party/protobuf/src/google/protobuf/field_mask.proto
diff --git a/third_party/protobuf/src/google/protobuf/field_mask.proto b/third_party/protobuf/src/google/protobuf/field_mask.proto
index 908c8a86d8205c1c04cf25d47ecd83200c6f7d80..6af6dbe89805963c66ae99be1b3affd0dcec8135 100644
--- a/third_party/protobuf/src/google/protobuf/field_mask.proto
+++ b/third_party/protobuf/src/google/protobuf/field_mask.proto
@@ -88,7 +88,7 @@ option java_generate_equals_and_hash = true;
 // operation applies to all fields (as if a FieldMask of all fields
 // had been specified).
 //
-// Note that a field mask does not necessarily applies to the
+// Note that a field mask does not necessarily apply to the
 // top-level response message. In case of a REST get operation, the
 // field mask applies directly to the response, but in case of a REST
 // list operation, the mask instead applies to each individual message
@@ -162,6 +162,32 @@ option java_generate_equals_and_hash = true;
 //       mask: "user.displayName,photo"
 //     }
 //
+// # Field Masks and Oneof Fields
+//
+// Field masks treat fields in oneofs just as regular fields. Consider the
+// following message:
+//
+//     message SampleMessage {
+//       oneof test_oneof {
+//         string name = 4;
+//         SubMessage sub_message = 9;
+//       }
+//     }
+//
+// The field mask can be:
+//
+//     mask {
+//       paths: "name"
+//     }
+//
+// Or:
+//
+//     mask {
+//       paths: "sub_message"
+//     }
+//
+// Note that oneof type names ("test_oneof" in this case) cannot be used in
+// paths.
 message FieldMask {
   // The set of field mask paths.
   repeated string paths = 1;