Merge pull request #1473 from elemoine/vector-api-zindex

[vector-api] Make canvas immediate API support zIndex

src/ol/renderer/canvas/canvaslayerrenderer.js

@@ -90,6 +90,7 @@ ol.renderer.canvas.Layer.prototype.dispatchComposeEvent_ =
     var composeEvent = new ol.render.Event(type, layer, render, frameState,
         context, null);
     layer.dispatchEvent(composeEvent);
+    render.flush();
   }
 };
 

src/ol/renderer/canvas/canvasmaprenderer.js

@@ -109,6 +109,7 @@ ol.renderer.canvas.Map.prototype.dispatchComposeEvent_ =
     var composeEvent = new ol.render.Event(type, map, render, frameState,
         context, null);
     map.dispatchEvent(composeEvent);
+    render.flush();
   }
 };