Add canvas style default values

src/ol/render/canvas/canvas.js

@@ -0,0 +1,19 @@
+goog.provide('ol.render.canvas');
+
+
+/**
+ * @const {string}
+ */
+ol.render.canvas.defaultFillStyle = 'black';
+
+
+/**
+ * @const {string}
+ */
+ol.render.canvas.defaultStrokeStyle = 'black';
+
+
+/**
+ * @const {number}
+ */
+ol.render.canvas.defaultLineWidth = 1;