Add abstract tag at class level

src/ol/format/feature.js

@@ -15,6 +15,7 @@ goog.require('ol.proj');
  * file formats.  See the documentation for each format for more details.
  *
  * @constructor
+ * @abstract
  * @api stable
  */
 ol.format.Feature = function() {

src/ol/format/gmlbase.js

@@ -31,6 +31,7 @@ goog.require('ol.xml');
  * ol.format.GML3.
  *
  * @constructor
+ * @abstract
  * @param {olx.format.GMLOptions=} opt_options
  *     Optional configuration object.
  * @extends {ol.format.XMLFeature}

src/ol/format/jsonfeature.js

@@ -12,6 +12,7 @@ goog.require('ol.format.FormatType');
  * Base class for JSON feature formats.
  *
  * @constructor
+ * @abstract
  * @extends {ol.format.Feature}
  */
 ol.format.JSONFeature = function() {

src/ol/format/textfeature.js

@@ -12,6 +12,7 @@ goog.require('ol.format.FormatType');
  * Base class for text feature formats.
  *
  * @constructor
+ * @abstract
  * @extends {ol.format.Feature}
  */
 ol.format.TextFeature = function() {

src/ol/format/xml.js

@@ -8,6 +8,7 @@ goog.require('ol.xml');
  * Generic format for reading non-feature XML data
  *
  * @constructor
+ * @abstract
  * @struct
  */
 ol.format.XML = function() {

src/ol/format/xmlfeature.js

@@ -14,6 +14,7 @@ goog.require('ol.xml');
  * Base class for XML feature formats.
  *
  * @constructor
+ * @abstract
  * @extends {ol.format.Feature}
  */
 ol.format.XMLFeature = function() {