fix(dialog): switch dialog to use disableScroll, fix focus trap

closes #2443

src/components/dialog/dialog.js

@@ -442,14 +442,6 @@ function MdDialogProvider($$interimElementProvider) {
       }
     };
 
-    function trapFocus(ev) {
-      var dialog = document.querySelector('md-dialog');
-
-      if (dialog && !dialog.contains(ev.target)) {
-        ev.stopImmediatePropagation();
-        dialog.focus();
-      }
-    }
 
     // On show method for dialogs
     function onShow(scope, element, options) {
@@ -484,11 +476,9 @@ function MdDialogProvider($$interimElementProvider) {
 
       configureAria(element.find('md-dialog'), role, options);
 
-      document.addEventListener('focus', trapFocus, true);
 
       if (options.disableParentScroll) {
-        options.lastOverflow = options.parent.css('overflow');
-        options.parent.css('overflow', 'hidden');
+        options.restoreScroll = $mdUtil.disableScrollAround(element);
       }
 
       return dialogPopIn(
@@ -546,8 +536,7 @@ function MdDialogProvider($$interimElementProvider) {
         $animate.leave(options.backdrop);
       }
       if (options.disableParentScroll) {
-        options.parent.css('overflow', options.lastOverflow);
-        delete options.lastOverflow;
+        options.restoreScroll();
       }
       if (options.escapeToClose) {
         $rootElement.off('keyup', options.rootElementKeyupCallback);
@@ -558,7 +547,6 @@ function MdDialogProvider($$interimElementProvider) {
 
       applyAriaToSiblings(element, false);
 
-      document.removeEventListener('focus', trapFocus, true);
 
       return dialogPopOut(
         element,