Do not expose ROLE_SYSTEM_WINDOW for our root object

Do not return ROLE_SYSTEM_WINDOW ourselves as that is a special MSAA
system role used to indicate a real native window object. It is
automatically created by oleacc.dll as a parent of the root of our
hierarchy, matching the HWND.

For AX_ROLE_WINDOW, we should expose something similar to what Firefox
exposes, namely ROLE_SYSTEM_APPLICATION.

This helps NVDA not read superfluous text when the user navigates
to the toolbar or location bar.

Bug: 794931
Change-Id: I123f07cb477304da1f016d65ea8c2b23b7a92ef4
Reviewed-on: https://chromium-review.googlesource.com/826866
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: Aaron Leventhal <aleventhal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#524102}

ui/accessibility/platform/ax_platform_node_win.cc

@@ -2914,7 +2914,11 @@ int AXPlatformNodeWin::MSAARole() {
       return ROLE_SYSTEM_GROUPING;
 
     case AX_ROLE_WINDOW:
-      return ROLE_SYSTEM_WINDOW;
+      // Do not return ROLE_SYSTEM_WINDOW as that is a special MSAA system role
+      // used to indicate a real native window object. It is automatically
+      // created by oleacc.dll as a parent of the root of our hierarchy,
+      // matching the HWND.
+      return ROLE_SYSTEM_APPLICATION;
 
     // TODO(dmazzoni): figure out the proper MSAA role for roles listed below.
     case AX_ROLE_BLOCKQUOTE:

ui/views/accessibility/native_view_accessibility_win_unittest.cc

@@ -280,5 +280,22 @@ TEST_F(NativeViewAccessibilityWinTest, GetAllOwnedWidgetsCrash) {
   EXPECT_EQ(1L, child_count);
 }
 
+TEST_F(NativeViewAccessibilityWinTest, WindowHasRoleApplication) {
+  // We expect that our internal window object does not expose
+  // ROLE_SYSTEM_WINDOW, but ROLE_SYSTEM_APPLICATION instead.
+  Widget widget;
+  Widget::InitParams init_params =
+      CreateParams(Widget::InitParams::TYPE_WINDOW);
+  init_params.ownership = Widget::InitParams::WIDGET_OWNS_NATIVE_WIDGET;
+  widget.Init(init_params);
+
+  ComPtr<IAccessible> accessible(
+      widget.GetRootView()->GetNativeViewAccessible());
+  ScopedVariant childid_self(CHILDID_SELF);
+  ScopedVariant role;
+  EXPECT_EQ(S_OK, accessible->get_accRole(childid_self, role.Receive()));
+  EXPECT_EQ(role.type(), VT_I4);
+  EXPECT_EQ(V_I4(role.ptr()), ROLE_SYSTEM_APPLICATION);
+}
 }  // namespace test
 }  // namespace views