added missing class DeviceDetectorFactory

core/DeviceDetectorFactory.php

+<?php
+/**
+ * Piwik - Open source web analytics
+ *
+ * @link http://piwik.org
+ * @license http://www.gnu.org/licenses/gpl-3.0.html GPL v3 or later
+ *
+ */
+namespace Piwik;
+
+use DeviceDetector\DeviceDetector;
+
+class DeviceDetectorFactory
+{
+    protected static $deviceDetectorInstances = array();
+
+    /**
+     * Returns a Singleton instance of DeviceDetector for the given user agent
+     * @param string $userAgent
+     * @return DeviceDetector
+     */
+    public static function getInstance($userAgent)
+    {
+        if (array_key_exists($userAgent, self::$deviceDetectorInstances)) {
+
+            return self::$deviceDetectorInstances[$userAgent];
+        }
+
+        $deviceDetector = new DeviceDetector($userAgent);
+        $deviceDetector->discardBotInformation();
+        $deviceDetector->setCache(new DeviceDetectorCache('tracker', 86400));
+        $deviceDetector->parse();
+
+        self::$deviceDetectorInstances[$userAgent] = $deviceDetector;
+
+        return $deviceDetector;
+    }
+
+}