Retina fix

[d3signerd]

$scope.generate = function() {
var ctx = element[0].getContext("2d");
ctx.canvas.width = $scope.references.self.width;
ctx.canvas.height = $scope.references.self.height;
$scope.instance = eval('new Chart(ctx).' +attr.isType+ '($scope.data,$scope.options)');
}