Bug 1644650 - Make the main developer tools window an application for assistive technologies again, r=nchevobbe

This broke when the main developer tools window was converted from XUL to XHTML. By adding the application role, the window is once again a window, not a document for the accessibility engine.

In addition, while I was here, I fixed the role of the focusable vbox because it is the first thing the user lands on when tabbing, to make it a semantic group, not an "unknown". Since this is probably supposed to be focusable for keyboard users, it is better to have an appropriate role.

Differential Revision: https://phabricator.services.mozilla.com/D79038

devtools/client/framework/toolbox.xhtml

@@ -11,7 +11,7 @@
 <!DOCTYPE window>
 <window xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
         xmlns:html="http://www.w3.org/1999/xhtml"
-        csp="default-src chrome: resource:; img-src chrome: resource: data:; object-src 'none'">
+        csp="default-src chrome: resource:; img-src chrome: resource: data:; object-src 'none'" role="application">
   <linkset>
     <html:link rel="localization" href="devtools/client/tooltips.ftl"/>
   </linkset>
@@ -23,7 +23,7 @@
   <script src="chrome://global/content/globalOverlay.js"/>
   <script src="chrome://devtools/content/framework/toolbox-init.js"/>
 
-  <vbox id="toolbox-container" flex="1">
+  <vbox id="toolbox-container" flex="1" role="group">
     <div xmlns="http://www.w3.org/1999/xhtml" id="toolbox-error-mount"/>
     <div xmlns="http://www.w3.org/1999/xhtml" id="toolbox-notificationbox"/>
     <div xmlns="http://www.w3.org/1999/xhtml" id="toolbox-toolbar-mount"