MD Settings: focus header when dialog shows to signal to AT what's going on

ui/webui/resources/cr_elements/cr_dialog/cr_dialog.js

Index: ui/webui/resources/cr_elements/cr_dialog/cr_dialog.js
diff --git a/ui/webui/resources/cr_elements/cr_dialog/cr_dialog.js b/ui/webui/resources/cr_elements/cr_dialog/cr_dialog.js
index d15ed9b8173a769d12afe886806d1509a99cfffc..3e29f9fcb60fe9ee6eb56748814f412c4397903d 100644
--- a/ui/webui/resources/cr_elements/cr_dialog/cr_dialog.js
+++ b/ui/webui/resources/cr_elements/cr_dialog/cr_dialog.js
@@ -41,6 +41,13 @@ Polymer({
     }.bind(this));
   },
 
+  /** @override */
+  attached: function() {
+    var title = this.getContentChildren('[select=".title"]');

[dpapad, 2017/02/24 20:46:10]

Nit(optional): Perhaps use queryEffectiveChildren instead which returns the 1st
occurrence instead of an array?

[Dan Beam, 2017/02/24 22:08:31]

that's different.  that gets all the distributed children.  i mean, it'd
probably functionally work because the first node with class="title" would
likely be in this slot and it'd be crazy to use class="title" inside of
class="body", but this is specifically looking for the first child of a specific
<content> slot

+    if (title.length)
+      title[0].tabIndex = -1;
+  },
+
   cancel: function() {
     this.fire('cancel');
     HTMLDialogElement.prototype.close.call(this, '');