Implement basic ShowItemInFolder for linux....

chrome/common/platform_util_mac.mm

Index: chrome/common/platform_util_mac.mm
===================================================================
--- chrome/common/platform_util_mac.mm	(revision 0)
+++ chrome/common/platform_util_mac.mm	(revision 0)
@@ -0,0 +1,16 @@
+// Copyright (c) 2009 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/common/platform_util.h"
+
+#include "base/file_path.h"
+#include "base/logging.h"
+
+namespace platform_util {
+
+void ShowItemInFolder(const FilePath& full_path) {
+  NOTIMPLEMENTED();
+}
+
+}  // namespace platform_util