Update //third_party/protobuf to version 3.

third_party/protobuf/java/src/main/java/com/google/protobuf/RpcCallback.java

Index: third_party/protobuf/java/src/main/java/com/google/protobuf/RpcCallback.java
diff --git a/third_party/protobuf/python/google/protobuf/internal/more_extensions_dynamic.proto b/third_party/protobuf/java/src/main/java/com/google/protobuf/RpcCallback.java
similarity index 69%
copy from third_party/protobuf/python/google/protobuf/internal/more_extensions_dynamic.proto
copy to third_party/protobuf/java/src/main/java/com/google/protobuf/RpcCallback.java
index df98ac4bd1929fda636c9e2fce1a9184ebf5d472..10752968e27f1e32c20dd34ed0e42a271fd59b2a 100644
--- a/third_party/protobuf/python/google/protobuf/internal/more_extensions_dynamic.proto
+++ b/third_party/protobuf/java/src/main/java/com/google/protobuf/RpcCallback.java
@@ -1,6 +1,6 @@
 // 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
@@ -28,22 +28,20 @@
 // (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: jasonh@google.com (Jason Hsueh)
-//
-// This file is used to test a corner case in the CPP implementation where the
-// generated C++ type is available for the extendee, but the extension is
-// defined in a file whose C++ type is not in the binary.
-
-
-import "google/protobuf/internal/more_extensions.proto";
-
-package google.protobuf.internal;
-
-message DynamicMessageType {
-  optional int32 a = 1;
-}
+package com.google.protobuf;
 
-extend ExtendedMessage {
-  optional int32 dynamic_int32_extension = 100;
-  optional DynamicMessageType dynamic_message_extension = 101;
+/**
+ * Interface for an RPC callback, normally called when an RPC completes.
+ * {@code ParameterType} is normally the method's response message type.
+ *
+ * <p>Starting with version 2.3.0, RPC implementations should not try to build
+ * on this, but should instead provide code generator plugins which generate
+ * code specific to the particular RPC implementation.  This way the generated
+ * code can be more appropriate for the implementation in use and can avoid
+ * unnecessary layers of indirection.
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+public interface RpcCallback<ParameterType> {
+  void run(ParameterType parameter);
 }