Giving vector layers the style they deserve

Now vector layers can have a style. ol.Style instances have an
apply method to get the symbolizer literals for a feature. If the
layer does not have a style defined, there is also a static
applyDefaultStyle function on ol.Style to get the default
symbolizer literals for a feature. The vector layer also got a
groupFeaturesBySymbolizerLiteral method, which returns an array
with features grouped by symbolizer, as needed by the canvas
renderer.

src/ol/style/shape.js

@@ -57,6 +57,19 @@ ol.style.ShapeLiteral = function(config) {
 goog.inherits(ol.style.ShapeLiteral, ol.style.PointLiteral);
 
 
+/**
+ * @inheritDoc
+ */
+ol.style.ShapeLiteral.prototype.equals = function(shapeLiteral) {
+  return this.type == shapeLiteral.type &&
+      this.size == shapeLiteral.size &&
+      this.fillStyle == shapeLiteral.fillStyle &&
+      this.strokeStyle == shapeLiteral.strokeStyle &&
+      this.strokeWidth == shapeLiteral.strokeWidth &&
+      this.opacity == shapeLiteral.opacity;
+};
+
+
 /**
  * @typedef {{type: (ol.style.ShapeType),
  *            size: (number|ol.Expression),