Don't expose the busy state on loading pages on Windows

crrev.com/c/3268209 introduced a regression for NVDA users:
When a page is newly-loaded, NVDA no longer announced the title
or did an automatic SayAll.

crrev.com/c/3585327 fixes the regression, but still exposes the busy
state all on documents in the process of loading. Doing this on
Windows can prevent NVDA from creating its virtual buffer during
page load.

This commit prevents the busy state from being exposed on a
document that already has content.

AX-Relnotes: Fixed regression causing newly-loaded pages from being
presented by NVDA.

(cherry picked from commit a86dd85)

Bug: 1315210
Change-Id: I0c73ef82ca29b286ceb7a628d7c47e13f93f0237
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3585368
Reviewed-by: Nektarios Paisios <nektar@chromium.org>
Reviewed-by: Aaron Leventhal <aleventhal@chromium.org>
Reviewed-by: Daniel Libby <dlibby@microsoft.com>
Commit-Queue: Joanmarie Diggs <jdiggs@igalia.com>
Cr-Original-Commit-Position: refs/heads/main@{#995109}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3607670
Auto-Submit: Joanmarie Diggs <jdiggs@igalia.com>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/branch-heads/5005@{#167}
Cr-Branched-From: 5b4d945-refs/heads/main@{#992738}

content/test/data/accessibility/event/navigation-api-expected-win.txt

@@ -1,4 +1,4 @@
-EVENT_OBJECT_STATECHANGE on <#document> role=ROLE_SYSTEM_DOCUMENT name="Starting title" value~=[doc-url] FOCUSED,BUSY,FOCUSABLE
+EVENT_OBJECT_STATECHANGE on <#document> role=ROLE_SYSTEM_DOCUMENT name="Starting title" value~=[doc-url] FOCUSED,FOCUSABLE
 === Start Continuation ===
 EVENT_OBJECT_HIDE on <p> role=ROLE_SYSTEM_GROUPING
 EVENT_OBJECT_REORDER on <main> role=ROLE_SYSTEM_GROUPING

ui/accessibility/platform/ax_platform_node_win.cc

@@ -7094,6 +7094,10 @@ bool AXPlatformNodeWin::IsNameExposed() const {
   }
 }
 
+bool AXPlatformNodeWin::IsPlatformDocumentWithContent() const {
+  return IsPlatformDocument() && GetChildCount();
+}
+
 bool AXPlatformNodeWin::IsUIAControl() const {
   // UIA provides multiple "views": raw, content and control. We only want to
   // populate the content and control views with items that make sense to
@@ -7327,8 +7331,14 @@ int AXPlatformNodeWin::MSAAState() const {
   // Map the ax::mojom::State to MSAA state. Note that some of the states are
   // not currently handled.
 
-  if (GetBoolAttribute(ax::mojom::BoolAttribute::kBusy))
+  // TODO(accessibility): https://crbug.com/1292018
+  // Exposing the busy state on the root web area means the NVDA user will end
+  // up without a virtualBuffer until the page fully loads. So if we have
+  // content, don't expose the busy state.
+  if (GetBoolAttribute(ax::mojom::BoolAttribute::kBusy) &&
+      !IsPlatformDocumentWithContent()) {
     msaa_state |= STATE_SYSTEM_BUSY;
+  }
 
   if (HasState(ax::mojom::State::kCollapsed))
     msaa_state |= STATE_SYSTEM_COLLAPSED;

ui/accessibility/platform/ax_platform_node_win.h

@@ -1282,6 +1282,8 @@ class AX_EXPORT __declspec(uuid("26f5641a-246d-457b-a96d-07f3fae6acf2"))
   int GetAnnotationTypeImpl() const;
   void AugmentNameWithImageAnnotationIfApplicable(std::wstring* name) const;
 
+  bool IsPlatformDocumentWithContent() const;
+
   // Get the value attribute as a Bstr, this means something different depending
   // on the type of element being queried. (e.g. kColorWell uses kColorValue).
   static BSTR GetValueAttributeAsBstr(AXPlatformNodeWin* target);