Allow literal from symbolizer without feature

src/ol/style/line.js

@@ -94,8 +94,12 @@ goog.inherits(ol.style.Line, ol.style.Symbolizer);
  * @inheritDoc
  * @return {ol.style.LineLiteral} Literal line symbolizer.
  */
-ol.style.Line.prototype.createLiteral = function(feature) {
+ol.style.Line.prototype.createLiteral = function(opt_feature) {
-  var attrs = feature.getAttributes();
+  var attrs,
+      feature = opt_feature;
+  if (goog.isDef(feature)) {
+    attrs = feature.getAttributes();
+  }
 
   var strokeStyle = this.strokeStyle_.evaluate(feature, attrs);
   goog.asserts.assertString(strokeStyle, 'strokeStyle must be a string');

src/ol/style/polygon.js

@@ -109,8 +109,12 @@ goog.inherits(ol.style.Polygon, ol.style.Symbolizer);
  * @inheritDoc
  * @return {ol.style.PolygonLiteral} Literal shape symbolizer.
  */
-ol.style.Polygon.prototype.createLiteral = function(feature) {
+ol.style.Polygon.prototype.createLiteral = function(opt_feature) {
-  var attrs = feature.getAttributes();
+  var attrs,
+      feature = opt_feature;
+  if (goog.isDef(feature)) {
+    attrs = feature.getAttributes();
+  }
 
   var fillStyle = this.fillStyle_.evaluate(feature, attrs);
   goog.asserts.assertString(fillStyle, 'fillStyle must be a string');

src/ol/style/shape.js

@@ -143,8 +143,12 @@ ol.style.Shape = function(options) {
  * @inheritDoc
  * @return {ol.style.ShapeLiteral} Literal shape symbolizer.
  */
-ol.style.Shape.prototype.createLiteral = function(feature) {
+ol.style.Shape.prototype.createLiteral = function(opt_feature) {
-  var attrs = feature.getAttributes();
+  var attrs,
+      feature = opt_feature;
+  if (goog.isDef(feature)) {
+    attrs = feature.getAttributes();
+  }
 
   var size = this.size_.evaluate(feature, attrs);
   goog.asserts.assertNumber(size, 'size must be a number');

src/ol/style/symbolizer.js

@@ -27,7 +27,7 @@ ol.style.Symbolizer = function() {};
 
 
 /**
- * @param {ol.Feature} feature Feature for evaluating expressions.
+ * @param {ol.Feature=} opt_feature Feature for evaluating expressions.
  * @return {ol.style.SymbolizerLiteral} Literal symbolizer.
  */
 ol.style.Symbolizer.prototype.createLiteral = goog.abstractMethod;