Add missing requires

Without explicit requires, it is possible that a build would exclude ol.js.

src/ol/renderer/canvas/canvasmaprenderer.js

@@ -6,6 +6,7 @@ goog.require('goog.asserts');
 goog.require('goog.dom');
 goog.require('goog.style');
 goog.require('goog.vec.Mat4');
+goog.require('ol');
 goog.require('ol.css');
 goog.require('ol.dom');
 goog.require('ol.layer.Image');