Support presentational iframes and make use of them in the uber frame.

content/browser/accessibility/browser_accessibility_win.cc

Index: content/browser/accessibility/browser_accessibility_win.cc
diff --git a/content/browser/accessibility/browser_accessibility_win.cc b/content/browser/accessibility/browser_accessibility_win.cc
index b269a07b49a38e6e3eb430d08196c962a02a5315..4575aa8c38b5e4908e1643a2514e14981f66d875 100644
--- a/content/browser/accessibility/browser_accessibility_win.cc
+++ b/content/browser/accessibility/browser_accessibility_win.cc
@@ -3088,6 +3088,14 @@ void BrowserAccessibilityWin::OnDataChanged() {
     relation->AddTarget(title_elem_id);
     relations_.push_back(relation);
   }
+
+  // If this is a web area for a presentational iframe, give it a role of
+  // something other than DOCUMENT so that the fact that it's a separate doc
+  // is not exposed to AT.
+  if (IsWebAreaForPresentationalIframe()) {
+    ia_role_ = ROLE_SYSTEM_GROUPING;
+    ia2_role_ = ROLE_SYSTEM_GROUPING;
+  }
 }
 
 void BrowserAccessibilityWin::OnUpdateFinished() {
@@ -3550,6 +3558,9 @@ void BrowserAccessibilityWin::InitRoleAndState() {
       ia2_role_ = IA2_ROLE_INTERNAL_FRAME;
       ia_state_ = STATE_SYSTEM_READONLY;
       break;
+    case ui::AX_ROLE_IFRAME_PRESENTATIONAL:
+      ia_role_ = ROLE_SYSTEM_GROUPING;
+      break;
     case ui::AX_ROLE_IMAGE:
       ia_role_ = ROLE_SYSTEM_GRAPHIC;
       ia_state_ |= STATE_SYSTEM_READONLY;