gdata: Add requestDirectoryRefresh to file_browser_private.

chrome/browser/chromeos/gdata/gdata_file_system.h

Index: chrome/browser/chromeos/gdata/gdata_file_system.h
diff --git a/chrome/browser/chromeos/gdata/gdata_file_system.h b/chrome/browser/chromeos/gdata/gdata_file_system.h
index 9ed98e96de87a8b013114796df4bfd67f554aa09..fb1fdc5557784eb21957a51e9c554568010f4219 100644
--- a/chrome/browser/chromeos/gdata/gdata_file_system.h
+++ b/chrome/browser/chromeos/gdata/gdata_file_system.h
@@ -365,6 +365,22 @@ class GDataFileSystemInterface {
       const FilePath& file_path,
       const ReadDirectoryCallback& callback) = 0;
 
+  // Requests a refresh of the directory pointed by |file_path| (i.e. fetches
+  // the latest metadata of files in the target directory).
+  //
+  // In particular, this function is used to get the latest thumbnail
+  // URLs. Thumbnail URLs change periodically even if contents of files are
+  // not changed, hence we should get the new thumbnail URLs manually if we
+  // detect that the existing thumnail URLs are stale.
+  //
+  // Upon success, the metadata of files in the target directory is updated,
+  // and the change is notified via Observer::OnDirectoryChanged(). Note that
+  // this function ignores changes in directories in the target
+  // directory. Changes in directories are handled via the delta feeds.
+  //
+  // Can be called from UI/IO thread.
+  virtual void RequestDirectoryRefresh(const FilePath& file_path) = 0;
+
   // Does server side content search for |search_query|. Search results will be
   // returned as gdata entries in temp directory proto, and their
   // title/file_name will be formatted as |<resource_id>.<original_file_name>|.
@@ -484,6 +500,8 @@ class GDataFileSystem : public GDataFileSystemInterface,
   virtual void ReadDirectoryByPathAsync(
       const FilePath& file_path,
       const ReadDirectoryCallback& callback) OVERRIDE;
+  virtual void RequestDirectoryRefresh(
+      const FilePath& file_path) OVERRIDE;
   virtual bool GetFileInfoByPath(const FilePath& file_path,
                                  GDataFileProperties* properties) OVERRIDE;
   virtual bool IsUnderGDataCacheDirectory(const FilePath& path) const OVERRIDE;
@@ -1402,6 +1420,10 @@ class GDataFileSystem : public GDataFileSystemInterface,
   void ReadDirectoryByPathAsyncOnUIThread(
       const FilePath& file_path,
       const ReadDirectoryCallback& callback);
+  void RequestDirectoryRefreshOnUIThread(
+      const FilePath& file_path);
+  void OnRequestDirectoryRefresh(GetDocumentsParams* params,
+                                 base::PlatformFileError error);
   void GetCacheStateOnUIThread(const std::string& resource_id,
                                const std::string& md5,
                                const GetCacheStateCallback& callback);