Add ol.webgl.Map.isImageTextureLoaded

src/ol/webgl/map.js

@@ -504,6 +504,15 @@ ol.webgl.Map.prototype.handleWebGLContextRestored = function() {
 };
 
 
+/**
+ * @param {Image} image Image.
+ * @return {boolean} Is image texture loaded.
+ */
+ol.webgl.Map.prototype.isImageTextureLoaded = function(image) {
+  return image.src in this.textureCache_[image.src];
+};
+
+
 /**
  * @inheritDoc
  */