angular 1.2以后（或更早？）移除了ng-bind-html-unsafe，那么我要用这个directive来绑定html代码怎么办？随便一测试，它是不支持把html直接传给它的：

    //html
   <p ng-bind-html="m"></p>

   //js
   $scope.m="<b>text</b>";

   //error:
   [$sce:unsafe] Attempting to use an unsafe value in a safe context.

参考这篇文章，得到解决。我选择的是直接做一个过滤器：

    //js
    app.filter(‘to_trusted‘, [‘$sce‘, function ($sce) {
            return function (text) {
                return $sce.trustAsHtml(text);
            };
        }]);
    app.controller...{
        $scope.m="<b>text</b>"
    }   
    //html:
    <p ng-bind-html="m | to_trusted"></p>

ng-bind-html-unsafe的替代