Try fast-fetch rather than full fetch if drive::FileSystem::GetEntryInfo failed.

chrome/browser/chromeos/drive/file_system.h

Index: chrome/browser/chromeos/drive/file_system.h
diff --git a/chrome/browser/chromeos/drive/file_system.h b/chrome/browser/chromeos/drive/file_system.h
index 6fb65198b21a0d394b6df1f33cb188c6ceb7014c..2d6ce08e0a45861768800def745ff8b0dd9b709d 100644
--- a/chrome/browser/chromeos/drive/file_system.h
+++ b/chrome/browser/chromeos/drive/file_system.h
@@ -323,16 +323,20 @@ class FileSystem : public FileSystemInterface,
       FileError error,
       scoped_ptr<DriveEntryProto> entry_proto);
 
-  // Part of ReadDirectoryByPath()
-  // 1) Called when ResourceMetadata::GetEntryInfoByPath() is complete.
-  // 2) Called when LoadIfNeeded() is complete.
-  // 3) Called when ResourceMetadata::ReadDirectoryByPath() is complete.
-  // |callback| must not be null.
-  void ReadDirectoryByPathAfterGetEntry(
+  // Loads the entry info of the children of |directory_path| to resource
+  // metadata. |callback| must not be null.
+  void LoadDirectoryIfNeeded(const base::FilePath& directory_path,
+                             const FileOperationCallback& callback);
+  void LoadDirectoryIfNeededAfterGetEntry(
       const base::FilePath& directory_path,
-      const ReadDirectoryWithSettingCallback& callback,
+      const FileOperationCallback& callback,
       FileError error,
       scoped_ptr<DriveEntryProto> entry_proto);
+
+  // Part of ReadDirectoryByPath()
+  // 1) Called when LoadDirectoryIfNeeded() is complete.
+  // 2) Called when ResourceMetadata::ReadDirectoryByPath() is complete.
+  // |callback| must not be null.
   void ReadDirectoryByPathAfterLoad(
       const base::FilePath& directory_path,
       const ReadDirectoryWithSettingCallback& callback,