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

chrome/browser/chromeos/drive/file_system.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_H_
 #define CHROME_BROWSER_CHROMEOS_DRIVE_FILE_SYSTEM_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 303 matching lines @@
       FileError error,
       scoped_ptr<ResourceEntry> entry);
   void GetEntryInfoByPathAfterLoad(const base::FilePath& file_path,
                                    const GetEntryInfoCallback& callback,
                                    FileError error);
   void GetEntryInfoByPathAfterGetEntry2(
       const GetEntryInfoCallback& callback,
       FileError error,
       scoped_ptr<ResourceEntry> entry);
 
+  // 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 FileOperationCallback& callback,
+      FileError error,
+      scoped_ptr<ResourceEntry> entry);
+
   // Part of ReadDirectoryByPath()
-  // 1) Called when ResourceMetadata::GetEntryInfoByPath() is complete.
-  // 2) Called when LoadIfNeeded() is complete.
-  // 3) Called when ResourceMetadata::ReadDirectoryByPath() is complete.
+  // 1) Called when LoadDirectoryIfNeeded() is complete.
+  // 2) Called when ResourceMetadata::ReadDirectoryByPath() is complete.
   // |callback| must not be null.
-  void ReadDirectoryByPathAfterGetEntry(
-      const base::FilePath& directory_path,
-      const ReadDirectoryWithSettingCallback& callback,
-      FileError error,
-      scoped_ptr<ResourceEntry> entry);
   void ReadDirectoryByPathAfterLoad(
       const base::FilePath& directory_path,
       const ReadDirectoryWithSettingCallback& callback,
       FileError error);
   void ReadDirectoryByPathAfterRead(
       const ReadDirectoryWithSettingCallback& callback,
       FileError error,
       scoped_ptr<ResourceEntryVector> entries);
 
   // Gets the file at |file_path| from the cache (if found in the cache),
@@ skipping 157 matching lines @@
   // Note: This should remain the last member so it'll be destroyed and
   // invalidate the weak pointers before any other members are destroyed.
   base::WeakPtrFactory<FileSystem> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(FileSystem);
 };
 
 }  // namespace drive
 
 #endif  // CHROME_BROWSER_CHROMEOS_DRIVE_FILE_SYSTEM_H_