Remove mojo::String.

content/browser/mime_registry_impl.cc

 // Copyright 2016 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 "content/browser/mime_registry_impl.h"
 
 #include "base/files/file_path.h"
 #include "base/memory/ptr_util.h"
 #include "content/public/browser/browser_thread.h"
 #include "mojo/common/common_type_converters.h"
@@ skipping 12 matching lines @@
   mojo::MakeStrongBinding(base::MakeUnique<MimeRegistryImpl>(),
                           std::move(request));
 }
 
 void MimeRegistryImpl::GetMimeTypeFromExtension(
     const std::string& extension,
     const GetMimeTypeFromExtensionCallback& callback) {
   DCHECK_CURRENTLY_ON(BrowserThread::FILE);
   std::string mime_type;
   net::GetMimeTypeFromExtension(
-      mojo::String(extension).To<base::FilePath::StringType>(), &mime_type);
+      base::FilePath::FromUTF8Unsafe(extension).value(), &mime_type);
   callback.Run(mime_type);
 }
 
 }  // namespace content