Implement ChromeOS mime type extension mappings.

net/base/mime_extension_chromeos.cc

+// Copyright 2015 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/mime_extension_chromeos.h"
+
+#include "base/logging.h"
+#include "net/base/mime_util.h"
+
+namespace chromeos {
+
+namespace {
+
+static const net::MimeInfo mimetype_extension_mapping[] = {
+    {"application/epub+zip", "epub"},
+    {"application/zip", "zip"},
+    {"text/calendar", "ics"},
+};
+}  // namespace
+
+// On linux, chrome uses xdgmime to read extension-mimetype database (e.g.
+// /usr/share/mime) and estimate mime type from extension. However ChromeOS does
+// not have such database in it, we use |mimetype_extension_mapping| to resolve
+// mime type on ChromeOS.
+bool GetPlatformMimeTypeFromExtension(const base::FilePath::StringType& ext,
+                                      std::string* mime_type) {
+  base::FilePath path_ext(ext);
+  const std::string ext_narrow_str = path_ext.AsUTF8Unsafe();
+  const char* result = net::FindMimeType(mimetype_extension_mapping,
+                                         arraysize(mimetype_extension_mapping),
+                                         ext_narrow_str.c_str());
+  if (result) {
+    *mime_type = result;
+    return true;
+  }
+
+  return false;
+}
+}  // namespace chromeos