fix(listItem): fix menu triggering proxy elements

fixes #4303

Author: rschmukler

src/components/list/list.js

@@ -64,7 +64,7 @@ function mdListDirective($mdTheming) {
  * </hljs>
  *
  */
-function mdListItemDirective($mdAria, $mdConstant, $timeout) {
+function mdListItemDirective($mdAria, $mdConstant, $mdUtil, $timeout) {
   var proxiedTypes = ['md-checkbox', 'md-switch'];
   return {
     restrict: 'E',
@@ -227,7 +227,8 @@ function mdListItemDirective($mdAria, $mdConstant, $timeout) {
 
         if (proxies.length && firstChild) {
           $element.children().eq(0).on('click', function(e) {
-            if (firstChild.contains(e.target)) {
+            var parentButton = $mdUtil.getClosest(e.target, 'BUTTON');
+            if (!parentButton && firstChild.contains(e.target)) {
               angular.forEach(proxies, function(proxy) {
                 if (e.target !== proxy && !proxy.contains(e.target)) {
                   angular.element(proxy).triggerHandler('click');