Enabled pressing TAB to cycle through the Omnibox results.

ui/base/keycodes/keyboard_codes_posix.h

 // 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.
 
 /*
  * Copyright (C) 2006 Michael Emmel mike.emmel@gmail.com. All rights reserved.
  * Copyright (C) 2008, 2009 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ skipping 19 matching lines @@
 
 #ifndef UI_BASE_KEYCODES_KEYBOARD_CODES_POSIX_H_
 #define UI_BASE_KEYCODES_KEYBOARD_CODES_POSIX_H_
 #pragma once
 
 namespace ui {
 
 typedef enum {
   VKEY_BACK = 0x08,
   VKEY_TAB = 0x09,
+  VKEY_BACKTAB = 0x0A,
   VKEY_CLEAR = 0x0C,
   VKEY_RETURN = 0x0D,
   VKEY_SHIFT = 0x10,
   VKEY_CONTROL = 0x11,
   VKEY_MENU = 0x12,
   VKEY_PAUSE = 0x13,
   VKEY_CAPITAL = 0x14,
   VKEY_KANA = 0x15,
   VKEY_HANGUL = 0x15,
   VKEY_JUNJA = 0x17,
@@ skipping 151 matching lines @@
   VKEY_ZOOM = 0xFB,
   VKEY_NONAME = 0xFC,
   VKEY_PA1 = 0xFD,
   VKEY_OEM_CLEAR = 0xFE,
   VKEY_UNKNOWN = 0
 } KeyboardCode;
 
 }  // namespace ui
 
 #endif  // UI_BASE_KEYCODES_KEYBOARD_CODES_POSIX_H_