feat(dialog): allow specifying parent by string selector.

src/components/dialog/dialog.js

@@ -463,7 +463,6 @@ function MdDialogProvider($$interimElementProvider) {
  * Show method for dialogs
  */
  function onShow(scope, element, options, controller) {
- element = $mdUtil.extractElementByName(element, 'md-dialog');
  angular.element($document[0].body).addClass('md-dialog-is-showing');
 
  wrapSimpleContent();
@@ -549,8 +548,11 @@ function MdDialogProvider($$interimElementProvider) {
  * unless overridden in the options.parent
  */
  function captureSourceAndParent(element, options) {
- var origin = {element: null, bounds: null, focus: angular.noop};
- options.origin = angular.extend({}, origin, options.origin || {});
+ options.origin = angular.extend({
+ element: null,
+ bounds: null,
+ focus: angular.noop
+ }, options.origin || {});
 
  var source = angular.element((options.targetEvent || {}).target);
  if (source && source.length) {
@@ -564,7 +566,14 @@ function MdDialogProvider($$interimElementProvider) {
  }
  }
 
- // In case the user provides a raw dom element, always wrap it in jqLite
+ // If the parent specifier is a simple string selector, then query for
+ // the DOM element.
+ if ( angular.isString(options.parent) ) {
+ var simpleSelector = options.parent;
+ container = $document[0].querySelectorAll(selector);
+ options.parent = container.length ? container[0] : null;
+ }
+ // If we have a reference to a raw dom element, always wrap it in jqLite
  options.parent = angular.element(options.parent || $rootElement);
 
  }