Fix race in BrowserAccessibilityManagerWin creation.

content/browser/accessibility/browser_accessibility_manager_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_manager_win.h"
 
 #include "base/command_line.h"
 #include "base/win/scoped_comptr.h"
 #include "base/win/windows_version.h"
 #include "content/browser/accessibility/browser_accessibility_state_impl.h"
@@ skipping 18 matching lines @@
   return static_cast<BrowserAccessibilityManagerWin*>(this);
 }
 
 BrowserAccessibilityManagerWin::BrowserAccessibilityManagerWin(
     LegacyRenderWidgetHostHWND* accessible_hwnd,
     IAccessible* parent_iaccessible,
     const ui::AXTreeUpdate& initial_tree,
     BrowserAccessibilityDelegate* delegate,
     BrowserAccessibilityFactory* factory)
     : BrowserAccessibilityManager(initial_tree, delegate, factory),
-      parent_hwnd_(accessible_hwnd->GetParent()),
       parent_iaccessible_(parent_iaccessible),
       tracked_scroll_object_(NULL),
       accessible_hwnd_(accessible_hwnd) {
-  accessible_hwnd_->set_browser_accessibility_manager(this);
+  if (accessible_hwnd_) {
+    accessible_hwnd_->set_browser_accessibility_manager(this);
+    parent_hwnd_ = accessible_hwnd->GetParent();
+  }
 }
 
 BrowserAccessibilityManagerWin::~BrowserAccessibilityManagerWin() {
   if (tracked_scroll_object_) {
     tracked_scroll_object_->Release();
     tracked_scroll_object_ = NULL;
   }
   if (accessible_hwnd_)
     accessible_hwnd_->OnManagerDeleted();
 }
 
 // static
 ui::AXTreeUpdate BrowserAccessibilityManagerWin::GetEmptyDocument() {
   ui::AXNodeData empty_document;
   empty_document.id = 0;
   empty_document.role = ui::AX_ROLE_ROOT_WEB_AREA;
   empty_document.state =
       (1 << ui::AX_STATE_ENABLED) |
       (1 << ui::AX_STATE_READ_ONLY) |
       (1 << ui::AX_STATE_BUSY);
 
   ui::AXTreeUpdate update;
   update.nodes.push_back(empty_document);
   return update;
 }
 
+void BrowserAccessibilityManagerWin::SetAccessibleHWND(
+    LegacyRenderWidgetHostHWND* accessible_hwnd) {
+  accessible_hwnd_ = accessible_hwnd;
+  accessible_hwnd_->set_browser_accessibility_manager(this);
+  parent_hwnd_ = accessible_hwnd->GetParent();
+}
+
 void BrowserAccessibilityManagerWin::MaybeCallNotifyWinEvent(DWORD event,
                                                              LONG child_id) {
   // Don't fire events if this view isn't hooked up to its parent.
-  if (!parent_iaccessible())
+  if (!parent_iaccessible() || !parent_hwnd())
     return;
 
   // If on Win 7 and complete accessibility is enabled, use the fake child HWND
   // to use as the root of the accessibility tree. See comments above
   // LegacyRenderWidgetHostHWND for details.
   if (BrowserAccessibilityStateImpl::GetInstance()->IsAccessibleBrowser()) {
     DCHECK(accessible_hwnd_);
     parent_hwnd_ = accessible_hwnd_->hwnd();
     parent_iaccessible_ = accessible_hwnd_->window_accessible();
   }
@@ skipping 175 matching lines @@
   // |parent_iaccessible_| are no longer valid either, since they were
   // derived from AccessibleHWND. We don't have to restore them to
   // previous values, though, because this should only happen
   // during the destruct sequence for this window.
   accessible_hwnd_ = NULL;
   parent_hwnd_ = NULL;
   parent_iaccessible_ = NULL;
 }
 
 }  // namespace content