deleteTexture method
Implementation
void deleteTexture(Texture texture) {
var textureProperties = properties.get(texture);
_gl.deleteTexture(textureProperties["__webglTexture"]);
var source = texture.source;
Map webglTextures = _sources.get(source);
webglTextures.remove(textureProperties["__cacheKey"]);
info.memory["textures"] = info.memory["textures"]! - 1;
}