Make chrome.fileSystem.chooseEntry work on Google Drive directories.

chrome/browser/chromeos/drive/file_system_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.
 
 #ifndef CHROME_BROWSER_CHROMEOS_DRIVE_FILE_SYSTEM_UTIL_H_
 #define CHROME_BROWSER_CHROMEOS_DRIVE_FILE_SYSTEM_UTIL_H_
 
 #include <string>
 
 #include "base/callback_forward.h"
@@ skipping 135 matching lines @@
 
 // Invokes |callback| on blocking thread pool, after converting virtual |path|
 // string like "/special/drive/foo.txt" to the concrete local cache file path.
 // After |callback| returns, the written content is synchronized to the server.
 //
 // The |path| must be a path under Drive. Must be called from UI thread.
 void PrepareWritableFileAndRun(Profile* profile,
                                const base::FilePath& path,
                                const PrepareWritableFileCallback& callback);
 
+// Checks whether a directory exists at the given Drive path |directory|.
+// Must be called from UI thread. The result will be called back to |callback|.
+void CheckDirectoryExists(Profile* profile,
+                          const base::FilePath& directory,
+                          const FileOperationCallback& callback);
+
 // Ensures the existence of |directory| of '/special/drive/foo'.  This will
 // create |directory| and its ancestors if they don't exist.  |callback| is
 // invoked after making sure that |directory| exists.  |callback| should
 // interpret error codes of either FILE_ERROR_OK or FILE_ERROR_EXISTS as
 // indicating that |directory| now exists.
 //
 // If |directory| is not a Drive path, it won't check the existence and just
 // runs |callback|.
 //
 // Must be called from UI thread.
@@ skipping 50 matching lines @@
   DRIVE_CONNECTED,
 };
 
 // Returns the Drive connection status for the |profile|.
 ConnectionStatusType GetDriveConnectionStatus(Profile* profile);
 
 }  // namespace util
 }  // namespace drive
 
 #endif  // CHROME_BROWSER_CHROMEOS_DRIVE_FILE_SYSTEM_UTIL_H_