[fsp] Add support for opening files.

chrome/browser/chromeos/file_system_provider/fake_provided_file_system.cc

 // Copyright 2014 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/chromeos/file_system_provider/fake_provided_file_system.h"
 
 #include <string>
 
 #include "base/files/file.h"
 #include "base/message_loop/message_loop_proxy.h"
@@ skipping 100 matching lines @@
                       0 /* size */,
                       "Tue May 22 00:40:50 UTC 2014");
 
     base::MessageLoopProxy::current()->PostTask(
         FROM_HERE,
         base::Bind(
             callback, base::File::FILE_OK, entry_list, false /* has_more */));
   }
 }
 
+void FakeProvidedFileSystem::OpenFile(
+    const base::FilePath& file_path,
+    OpenFileMode mode,
+    bool create,
+    const fileapi::AsyncFileUtil::StatusCallback& callback) {
+  if (file_path.AsUTF8Unsafe() != "/hello.txt" ||
+      mode == OPEN_FILE_MODE_WRITE || create) {
+    callback.Run(base::File::FILE_ERROR_SECURITY);
+    return;
+  }
+
+  callback.Run(base::File::FILE_OK);
+}
+
 const ProvidedFileSystemInfo& FakeProvidedFileSystem::GetFileSystemInfo()
     const {
   return file_system_info_;
 }
 
 RequestManager* FakeProvidedFileSystem::GetRequestManager() {
   NOTREACHED();
   return NULL;
 }
 
 ProvidedFileSystemInterface* FakeProvidedFileSystem::Create(
     extensions::EventRouter* event_router,
     const ProvidedFileSystemInfo& file_system_info) {
   return new FakeProvidedFileSystem(file_system_info);
 }
 
 }  // namespace file_system_provider
 }  // namespace chromeos