Pass context instead of canvas when creating ol.renderer.canvas.Vector

src/ol/renderer/canvas/canvasvectorlayerrenderer.js

@@ -456,8 +456,10 @@ ol.renderer.canvas.VectorLayer.prototype.prepareFrame =
   sketchCanvas.width = sketchWidth;
   sketchCanvas.height = sketchHeight;
 
+  var sketchContext = /** @type {CanvasRenderingContext2D} */
+      (sketchCanvas.getContext('2d'));
   var sketchCanvasRenderer = new ol.renderer.canvas.Vector(
-      sketchCanvas, sketchTransform, this.requestMapRenderFrame_);
+      sketchContext, sketchTransform, this.requestMapRenderFrame_);
 
   // clear/resize final canvas
   var finalCanvas = this.canvas_;

src/ol/renderer/canvas/canvasvectorlayerrenderer2.js

@@ -150,7 +150,9 @@ ol.renderer.canvas.VectorLayer2.prototype.prepareFrame =
         -(origin[0] + halfWidth * viewResolution),
         -(origin[1] - halfHeight * viewResolution),
         0);
-    var renderer = new ol.renderer.canvas.Vector(canvas, coordsTransform,
+    var context = /** @type {CanvasRenderingContext2D} */
+        (canvas.getContext('2d'));
+    var renderer = new ol.renderer.canvas.Vector(context, coordsTransform,
         this.requestMapRenderFrame_);
 
     var groups = vectorLayer.groupFeaturesBySymbolizerLiteral(features,

src/ol/renderer/canvas/canvasvectorrenderer.js

@@ -31,16 +31,14 @@ goog.require('ol.style.TextLiteral');
 
 /**
  * @constructor
- * @param {HTMLCanvasElement} canvas Target canvas.
+ * @param {CanvasRenderingContext2D} context Context.
  * @param {goog.vec.Mat4.Number} transform Transform.
  * @param {function()=} opt_iconLoadedCallback Callback for deferred rendering
  *     when images need to be loaded before rendering.
  */
 ol.renderer.canvas.Vector =
-    function(canvas, transform, opt_iconLoadedCallback) {
+    function(context, transform, opt_iconLoadedCallback) {
 
-  var context = /** @type {CanvasRenderingContext2D} */
-      (canvas.getContext('2d'));
   /**
    * @type {goog.vec.Mat4.Number}
    * @private