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

third_party/protobuf/src/google/protobuf/any.h

Index: third_party/protobuf/src/google/protobuf/any.h
diff --git a/third_party/protobuf/src/google/protobuf/any.h b/third_party/protobuf/src/google/protobuf/any.h
index c8dbef1301c105398e82538faf6d42f797848576..04e541667f458c7287b6c951b13ae08d5669308e 100644
--- a/third_party/protobuf/src/google/protobuf/any.h
+++ b/third_party/protobuf/src/google/protobuf/any.h
@@ -50,10 +50,26 @@ class LIBPROTOBUF_EXPORT AnyMetadata {
   // AnyMetadata does not take ownership of "type_url" and "value".
   AnyMetadata(UrlType* type_url, ValueType* value);
 
+  // Packs a message using the default type URL prefix: "type.googleapis.com".
+  // The resulted type URL will be "type.googleapis.com/<message_full_name>".
   void PackFrom(const Message& message);
-
+  // Packs a message using the given type URL prefix. The type URL will be
+  // constructed by concatenating the message type's full name to the prefix
+  // with an optional "/" separator if the prefix doesn't already end up "/".
+  // For example, both PackFrom(message, "type.googleapis.com") and
+  // PackFrom(message, "type.googleapis.com/") yield the same result type
+  // URL: "type.googleapis.com/<message_full_name>".
+  void PackFrom(const Message& message, const string& type_url_prefix);
+
+  // Unpacks the payload into the given message. Returns false if the message's
+  // type doesn't match the type specified in the type URL (i.e., the full
+  // name after the last "/" of the type URL doesn't match the message's actaul
+  // full name) or parsing the payload has failed.
   bool UnpackTo(Message* message) const;
 
+  // Checks whether the type specified in the type URL matches the given type.
+  // A type is consdiered matching if its full name matches the full name after
+  // the last "/" in the type URL.
   template<typename T>
   bool Is() const {
     return InternalIs(T::default_instance().GetDescriptor());