Linux: add GYP flag to build with system libbz2.

net/base/bzip2_filter_unittest.cc

 // Copyright (c) 2006-2008 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 <fstream>
 #include <iostream>
 
+#if defined(USE_SYSTEM_LIBBZ2)
+#include <bzlib.h>
+#else
+#include "third_party/bzip2/bzlib.h"
+#endif
+
 #include "base/file_util.h"
 #include "base/path_service.h"
 #include "base/scoped_ptr.h"
 #include "net/base/bzip2_filter.h"
 #include "net/base/filter_unittest.h"
 #include "net/base/io_buffer.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/platform_test.h"
-#include "third_party/bzip2/bzlib.h"
 
 namespace {
 
 const char* kExtraData = "Test Data, More Test Data, Even More Data of Test";
 const int kExtraDataBufferSize = 49;
 const int kDefaultBufferSize = 4096;
 const int kSmallBufferSize = 128;
 const int kMaxBufferSize = 1048576;    // 1048576 == 2^20 == 1 MB
 
 const char kApplicationOctetStream[] = "application/octet-stream";
@@ skipping 365 matching lines @@
   DecodeAndCompareWithFilter(filter.get(),
                              source_buffer(),
                              source_len() + kExtraDataBufferSize,
                              more_data,
                              more_data_len,
                              kDefaultBufferSize,
                              true);
 }
 
 }  // namespace