Use IAccessible2 to detect screen reader in Win Aura

content/browser/accessibility/browser_accessibility_win.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/accessibility/browser_accessibility_win.h"
 
 #include <UIAutomationClient.h>
 #include <UIAutomationCoreApi.h>
 
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/win/enum_variant.h"
 #include "base/win/scoped_comptr.h"
 #include "base/win/windows_version.h"
 #include "content/browser/accessibility/browser_accessibility_manager_win.h"
+#include "content/browser/accessibility/browser_accessibility_state_impl.h"
 #include "content/common/accessibility_messages.h"
 #include "content/public/common/content_client.h"
 #include "ui/base/accessibility/accessible_text_utils.h"
 #include "ui/base/win/accessibility_ids_win.h"
 #include "ui/base/win/accessibility_misc_utils.h"
 
 namespace content {
 
 // These nonstandard GUIDs are taken directly from the Mozilla sources
 // (accessible/src/msaa/nsAccessNodeWrap.cpp); some documentation is here:
@@ skipping 2616 matching lines @@
 //
 // IServiceProvider methods.
 //
 
 STDMETHODIMP BrowserAccessibilityWin::QueryService(REFGUID guidService,
                                                    REFIID riid,
                                                    void** object) {
   if (!instance_active_)
     return E_FAIL;
 
+  // The system uses IAccessible APIs for many purposes, but only
+  // assistive technology like screen readers uses IAccessible2.
+  // Enable full accessibility support when IAccessible2 APIs are queried.
+  if (riid == IID_IAccessible2)
+    BrowserAccessibilityStateImpl::GetInstance()->EnableAccessibility();
+
   if (guidService == GUID_IAccessibleContentDocument) {
     // Special Mozilla extension: return the accessible for the root document.
     // Screen readers use this to distinguish between a document loaded event
     // on the root document vs on an iframe.
     return manager_->GetRoot()->ToBrowserAccessibilityWin()->QueryInterface(
         IID_IAccessible2, object);
   }
 
   if (guidService == IID_IAccessible ||
       guidService == IID_IAccessible2 ||
@@ skipping 990 matching lines @@
   // The role should always be set.
   DCHECK(!role_name_.empty() || ia_role_);
 
   // If we didn't explicitly set the IAccessible2 role, make it the same
   // as the MSAA role.
   if (!ia2_role_)
     ia2_role_ = ia_role_;
 }
 
 }  // namespace content