Some classes with __get() method also need __set().

See #27881, #22234.

Built from https://develop.svn.wordpress.org/trunk@28521


git-svn-id: http://core.svn.wordpress.org/trunk@28347 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/custom-background.php

@@ -69,6 +69,19 @@ class Custom_Background {
 		return $this->$name;
 	}
 
+	/**
+	 * Make private properties setable for backwards compatibility
+	 *
+	 * @since 4.0.0
+	 * @param string $name
+	 * @param string $value
+	 * @return mixed
+	 */
+	public function __set( $name, $value ) {
+		return $this->$name = $value;
+	}
+
+
 	/**
 	 * Set up the hooks for the Custom Background admin page.
 	 *