Fix dropdown direction issue on webkit

issue angular-ui#1016

Author: pulse14

src/uiSelectDirective.js

@@ -1,6 +1,6 @@
 uis.directive('uiSelect',
-  ['$document', 'uiSelectConfig', 'uiSelectMinErr', 'uisOffset', '$compile', '$parse', '$timeout',
-  function($document, uiSelectConfig, uiSelectMinErr, uisOffset, $compile, $parse, $timeout) {
+  ['$document', '$window', 'uiSelectConfig', 'uiSelectMinErr', 'uisOffset', '$compile', '$parse', '$timeout',
+  function($document, $window, uiSelectConfig, uiSelectMinErr, uisOffset, $compile, $parse, $timeout) {
 
   return {
     restrict: 'EA',
@@ -270,7 +270,7 @@ uis.directive('uiSelect',
               var offsetDropdown = uisOffset(dropdown);
 
               // Determine if the direction of the dropdown needs to be changed.
-              if (offset.top + offset.height + offsetDropdown.height > $document[0].documentElement.scrollTop + $document[0].documentElement.clientHeight) {
+              if (offset.top + offset.height + offsetDropdown.height > $window.pageYOffset + $document[0].documentElement.clientHeight) {
                 dropdown[0].style.position = 'absolute';
                 dropdown[0].style.top = (offsetDropdown.height * -1) + 'px';
                 element.addClass(directionUpClassName);