Prepare to use generated shim headers for speex

speex.h

Index: speex.h
===================================================================
--- speex.h	(revision 160092)
+++ speex.h	(working copy)
@@ -1,22 +0,0 @@
-// 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.
-
-#ifndef THIRD_PARTY_SPEEX_SPEEX_H_
-#define THIRD_PARTY_SPEEX_SPEEX_H_
-#pragma once
-
-// This is a shim header to include the right speex header.
-// Use this instead of referencing the speex header directly.
-
-#if defined(USE_SYSTEM_SPEEX)
-#include <speex/speex.h>
-#include <speex/speex_callbacks.h>
-#include <speex/speex_stereo.h>
-#else
-#include "third_party/speex/include/speex/speex.h"
-#include "third_party/speex/include/speex/speex_callbacks.h"
-#include "third_party/speex/include/speex/speex_stereo.h"
-#endif
-
-#endif  // THIRD_PARTY_SPEEX_SPEEX_H_