[Media Gallery] Added code to support mtp device media file system on Windows.

chrome/browser/media_gallery/win/mtp_device_operations_util.h

+// Copyright (c) 2012 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.
+
+// This file contains util functions to support media filesystem operations.
+// It has several utility functions to open a media transfer protocol (MTP)
+// device for communication, to enumerate the device contents, to read the
+// device file object, etc. All these tasks may take an arbitary long time
+// to complete. This file segregates those functionalities and runs them
+// in the blocking pool thread rather than in the UI thread.
+
+#ifndef CHROME_BROWSER_MEDIA_GALLERY_WIN_MTP_DEVICE_OPERATIONS_UTIL_H_
+#define CHROME_BROWSER_MEDIA_GALLERY_WIN_MTP_DEVICE_OPERATIONS_UTIL_H_
+
+#include <portabledeviceapi.h>
+#include <string>
+
+#include "base/platform_file.h"
+#include "base/string16.h"
+#include "base/win/scoped_comptr.h"
+#include "chrome/browser/media_gallery/win/mtp_device_object_entry.h"
+
+namespace chrome {
+
+namespace media_transfer_protocol {
+
+// Opens the device for communication. |pnp_device_id| specifies the plug and
+// play device ID string. On success, returns true and updates |device| with
+// the portable device interface.
+bool OpenDevice(const string16& pnp_device_id,
+                base::win::ScopedComPtr<IPortableDevice>* device);

[Lei Zhang, 2013/01/14 23:25:30]

You can return a NULL ScopedComPtr right? If so, there's no need to have
|device| as an out param. Just return NULL to indicate failure.

[kmadhusu, 2013/01/15 19:08:17]

Done.

+
+// Gets the details of the object specified by |object_id| from the given MTP
+// |device|. On success, returns no error (base::PLATFORM_FILE_OK) and fills in
+// |file_entry_info|. On failure, returns the corresponding platform file error
+// and |file_entry_info| is not set.
+base::PlatformFileError GetFileEntryInfo(
+    IPortableDevice* device,
+    const string16& object_id,
+    base::PlatformFileInfo* file_entry_info);
+
+// Gets the entries of the directory specified by |directory_object_id| from
+// the given MTP |device|. On success, returns true and fills in
+// |object_entries|. On failure, returns false and |object_entries| is not
+// set.
+bool GetDirectoryEntries(IPortableDevice* device,
+                         const string16& directory_object_id,
+                         MTPDeviceObjectEntries* object_entries);
+
+// Writes the data of the object specified by |file_object_id| from the given
+// MTP |device| to the file specified by |local_path|. On success, returns
+// true and writes the object data in |local_path|. On failure, returns false.
+bool WriteFileObjectData(IPortableDevice* device,

[Lei Zhang, 2013/01/14 23:25:30]

Can you rename this to WriteFileObjectContentToPath ? "WriteFileObjectData"
sounds like it is trying to save data into a file object.

[kmadhusu, 2013/01/15 19:08:17]

Done.

+                         const string16& file_object_id,
+                         const FilePath& local_path);
+
+// Returns the identifier of the object specified by the |object_name|.

[Lei Zhang, 2013/01/14 23:25:30]

Is |object_name| the friendly name?

[kmadhusu, 2013/01/15 19:08:17]

Yes.

+// |parent_id| specifies the object's parent identifier.
+string16 GetObjectIdFromName(IPortableDevice* device,
+                             const string16& parent_id,
+                             const string16& object_name);
+
+}  // namespace media_transfer_protocol
+
+}  // namespace chrome
+
+#endif  // CHROME_BROWSER_MEDIA_GALLERY_WIN_MTP_DEVICE_OPERATIONS_UTIL_H_