Add a GetSignature() method to dbus::MessageReader.

dbus/message.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef DBUS_MESSAGE_H_
 #define DBUS_MESSAGE_H_
 
 #include <string>
 #include <vector>
 #include <dbus/dbus.h>
@@ skipping 93 matching lines @@
   // SetSignature() does not exist as we cannot do it.
 
   // Gets the destination, the path, the interface, the member, etc.
   // If not set, an empty string is returned.
   std::string GetDestination();
   ObjectPath GetPath();
   std::string GetInterface();
   std::string GetMember();
   std::string GetErrorName();
   std::string GetSender();
-  std::string GetSignature();
+  std::string GetDataSignature();
   // Gets the serial and reply serial numbers. Returns 0 if not set.
   uint32 GetSerial();
   uint32 GetReplySerial();
 
   // Returns the string representation of this message. Useful for
   // debugging. The output is truncated as needed (ex. strings are truncated
   // if longer than a certain limit defined in the .cc file).
   std::string ToString();
 
  protected:
@@ skipping 331 matching lines @@
   bool PopVariantOfUint64(uint64* value);
   bool PopVariantOfDouble(double* value);
   bool PopVariantOfString(std::string* value);
   bool PopVariantOfObjectPath(ObjectPath* value);
 
   // Get the data type of the value at the current iterator
   // position. INVALID_DATA will be returned if the iterator points to the
   // end of the message.
   Message::DataType GetDataType();
 
+  // Get the DBus signature of the value at the current iterator position.
+  // An empty string will be returned if the iterator points to the end of
+  // the message.
+  std::string GetDataSignature();
+
  private:
   // Returns true if the data type at the current iterator position
   // matches the given D-Bus type, such as DBUS_TYPE_BYTE.
   bool CheckDataType(int dbus_type);
 
   // Helper function used to implement PopByte() etc.
   bool PopBasic(int dbus_type, void *value);
 
   // Helper function used to implement PopArray() etc.
   bool PopContainer(int dbus_type, MessageReader* sub_reader);
 
   // Helper function used to implement PopVariantOfByte() etc.
   bool PopVariantOfBasic(int dbus_type, void* value);
 
   Message* message_;
   DBusMessageIter raw_message_iter_;
 
   DISALLOW_COPY_AND_ASSIGN(MessageReader);
 };
 
 }  // namespace dbus
 
 #endif  // DBUS_MESSAGE_H_