refactor(ngCsp): use document.head

The `head` property is available from IE9 onwards.

Closes angular#11905

Author: realityking

lib/grunt/utils.js

@@ -116,7 +116,7 @@ module.exports = {
         .replace(/\\/g, '\\\\')
         .replace(/'/g, "\\'")
         .replace(/\r?\n/g, '\\n');
-      js = "!window.angular.$$csp() && window.angular.element(document).find('head').prepend('<style type=\"text/css\">" + css + "</style>');";
+      js = "!window.angular.$$csp() && window.angular.element(document.head).prepend('<style type=\"text/css\">" + css + "</style>');";
       state.js.push(js);
 
       return state;