Make `chrome` target build without unused data members on Linux.

chrome/browser/extensions/api/messaging/native_process_launcher.cc

 // Copyright (c) 2012 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/extensions/api/messaging/native_process_launcher.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/callback.h"
@@ skipping 60 matching lines @@
     void CallCallbackOnIOThread(const LaunchedCallback& callback,
                                 LaunchResult result,
                                 base::Process process,
                                 base::File read_file,
                                 base::File write_file);
 
     bool detached_;
 
     bool allow_user_level_hosts_;
 
+#if defined(OS_WIN)
     // Handle of the native window corresponding to the extension.
     intptr_t window_handle_;
+#endif // OS_WIN
 
     DISALLOW_COPY_AND_ASSIGN(Core);
   };
 
   scoped_refptr<Core> core_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeProcessLauncherImpl);
 };
 
 NativeProcessLauncherImpl::Core::Core(bool allow_user_level_hosts,
                                       intptr_t window_handle)
     : detached_(false),
-      allow_user_level_hosts_(allow_user_level_hosts),
-      window_handle_(window_handle) {
-}
+      allow_user_level_hosts_(allow_user_level_hosts)
+#if defined(OS_WIN)
+      , window_handle_(window_handle)
+#endif // OS_WIN
+{}
 
 NativeProcessLauncherImpl::Core::~Core() {
   DCHECK(detached_);
 }
 
 void NativeProcessLauncherImpl::Core::Detach() {
   DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
   detached_ = true;
 }
 
@@ skipping 160 matching lines @@
   intptr_t window_handle = 0;
 #if defined(OS_WIN)
   window_handle = reinterpret_cast<intptr_t>(
       views::HWNDForNativeView(native_view));
 #endif
   return scoped_ptr<NativeProcessLauncher>(
       new NativeProcessLauncherImpl(allow_user_level_hosts, window_handle));
 }
 
 }  // namespace extensions