stub impl of linux,mac icon loader/manager

chrome/browser/icon_manager_win.cc

+// 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/browser/icon_manager.h"
+
+#include "base/file_path.h"
+
+IconGroupId IconManager::GetGroupIDFromFilepath(const FilePath& filepath) {
+  std::wstring extension = file_util::GetFileExtensionFromPath(filepath);
+  if (extension != L"exe" && extension != L"dll" && extension != L"ico")
+    return L'.' + extension;
+  else
+    return filepath.value();
+}