Extract and dispatch device uuid in media device attached notification message.

chromeos/dbus/cros_disks_client.h

Index: chromeos/dbus/cros_disks_client.h
diff --git a/chromeos/dbus/cros_disks_client.h b/chromeos/dbus/cros_disks_client.h
index 5d15f688f420f4955445a4f995145f1553f68221..7338111c6905fb01bd21a2b0d1d75be1a2bd9945 100644
--- a/chromeos/dbus/cros_disks_client.h
+++ b/chromeos/dbus/cros_disks_client.h
@@ -110,6 +110,9 @@ class DiskInfo {
   // Returns true if the device should be hidden from the file browser.
   bool is_hidden() const { return is_hidden_; }
 
+  // Returns file system uuid.
+  std::string uuid() const { return uuid_; }
+
  private:
   void InitializeFromResponse(dbus::Response* response);
 
@@ -127,6 +130,7 @@ class DiskInfo {
   uint64 total_size_in_bytes_;
   bool is_read_only_;
   bool is_hidden_;
+  std::string uuid_;
 };
 
 // A class to make the actual DBus calls for cros-disks service.