Use generated shim headers for zlib.

net/base/gzip_header.cc

 // 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 "net/base/gzip_header.h"
 
-#if defined(USE_SYSTEM_ZLIB)
-#include <zlib.h>
-#else
-#include "third_party/zlib/zlib.h"  // for Z_DEFAULT_COMPRESSION
-#endif
-
 #include "base/logging.h"
+#include "third_party/zlib/zlib.h"
 
 namespace net {
 
 const uint8 GZipHeader::magic[] = { 0x1f, 0x8b };
 
 GZipHeader::GZipHeader() {
   Reset();
 }
 
 GZipHeader::~GZipHeader() {
@@ skipping 151 matching lines @@
 
   if ( (state_ > IN_HEADER_OS) && (flags_ == 0) ) {
     *header_end = reinterpret_cast<const char*>(pos);
     return COMPLETE_HEADER;
   } else {
     return INCOMPLETE_HEADER;
   }
 }
 
 }  // namespace net