Prevent VoiceOver from announcing omnibox and status bubble overlay windows.

chrome/browser/ui/cocoa/omnibox/omnibox_popup_view_mac.mm

 // Copyright (c) 2011 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 "chrome/browser/ui/cocoa/omnibox/omnibox_popup_view_mac.h"
 
 #include <cmath>
 
 #include "base/stl_util.h"
 #include "base/sys_string_conversions.h"
@@ skipping 326 matching lines @@
     [popup_ setHasShadow:YES];
     [popup_ setLevel:NSNormalWindowLevel];
 
     scoped_nsobject<AutocompleteMatrix> matrix(
         [[AutocompleteMatrix alloc] initWithPopupView:this]);
     scoped_nsobject<OmniboxPopupView> contentView(
         [[OmniboxPopupView alloc] initWithFrame:NSZeroRect]);
 
     [contentView addSubview:matrix];
     [popup_ setContentView:contentView];
+
+    // TODO(dtseng): Ignore until we provide NSAccessibility support.
+    [popup_ accessibilitySetOverrideValue:NSAccessibilityUnknownRole
+        forAttribute:NSAccessibilityRoleAttribute];
   }
 }
 
 void OmniboxPopupViewMac::PositionPopup(const CGFloat matrixHeight) {
   // Calculate the popup's position on the screen.  It should abut the
   // field's visual border vertically, and be below the bounds
   // horizontally.
 
   // Start with the field's rect on the screen.
   NSRect popupFrame = NSInsetRect([field_ bounds], 0.0, kFieldVisualInset);
@@ skipping 463 matching lines @@
                         bottomLeftCornerRadius:kPopupRoundingRadius
                        bottomRightCornerRadius:kPopupRoundingRadius];
 
   // Draw the matrix clipped to our border.
   gfx::ScopedNSGraphicsContextSaveGState scopedGState;
   [path addClip];
   [super drawRect:rect];
 }
 
 @end