On the Mac, AX_EVENT_LOAD_COMPLETE should only be fired on the top document.

content/browser/renderer_host/render_widget_host_view_mac.mm

 // 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/renderer_host/render_widget_host_view_mac.h"
 
 #import <objc/runtime.h>
 #include <OpenGL/gl.h>
 #include <QuartzCore/QuartzCore.h>
 #include <stdint.h>
@@ skipping 1543 matching lines @@
   NSPoint origin = NSMakePoint(bounds.x(), bounds.y());
   NSSize size = NSMakeSize(bounds.width(), bounds.height());
   origin.y = NSHeight([cocoa_view_ bounds]) - origin.y;
   NSPoint originInWindow = [cocoa_view_ convertPoint:origin toView:nil];
   NSPoint originInScreen =
       ui::ConvertPointFromWindowToScreen([cocoa_view_ window], originInWindow);
   originInScreen.y = originInScreen.y - size.height;
   return gfx::Point(originInScreen.x, originInScreen.y);
 }
 
+NSView* RenderWidgetHostViewMac::AccessibilityGetAcceleratedWidget() {
+  return cocoa_view_;
+}
+
 void RenderWidgetHostViewMac::SetTextInputActive(bool active) {
   if (active) {
     if (GetTextInputType() == ui::TEXT_INPUT_TYPE_PASSWORD)
       EnablePasswordInput();
     else
       DisablePasswordInput();
   } else {
     if (GetTextInputType() == ui::TEXT_INPUT_TYPE_PASSWORD)
       DisablePasswordInput();
   }
@@ skipping 1687 matching lines @@
 
 // "-webkit-app-region: drag | no-drag" is implemented on Mac by excluding
 // regions that are not draggable. (See ControlRegionView in
 // native_app_window_cocoa.mm). This requires the render host view to be
 // draggable by default.
 - (BOOL)mouseDownCanMoveWindow {
   return YES;
 }
 
 @end