Proxy Constructor for peer proxy.
 Add new Constructor to create a peer proxy which is used to send a signal from dbus client (chromium).

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/2133004
diff --git a/chromeos/dbus/dbus.h b/chromeos/dbus/dbus.h
index af8b5dc..4775867 100644
--- a/chromeos/dbus/dbus.h
+++ b/chromeos/dbus/dbus.h
@@ -105,6 +105,13 @@
       : object_(GetGProxy(connection, name, path, interface, false)) {
   }
 
+  // Creates a peer proxy using dbus_g_proxy_new_for_peer.
+  Proxy(const BusConnection& connection,
+        const char* path,
+        const char* interface)
+      : object_(GetGPeerProxy(connection, path, interface)) {
+  }
+
   Proxy(const Proxy& x)
       : object_(x.object_) {
     if (object_)
@@ -145,6 +152,10 @@
                               const char* interface,
                               bool connect_to_name_owner);
 
+  static value_type GetGPeerProxy(const BusConnection& connection,
+                                  const char* path,
+                                  const char* interface);
+
   operator int() const;  // for safe bool cast
   friend void swap(Proxy& x, Proxy& y);