drive: Add the local largest changestamp to chrome:drive-internals

chrome/browser/chromeos/drive/drive_file_system_interface.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_DRIVE_FILE_SYSTEM_INTERFACE_H_
 #define CHROME_BROWSER_CHROMEOS_DRIVE_DRIVE_FILE_SYSTEM_INTERFACE_H_
 
 #include <string>
 #include <vector>
 
 #include "base/memory/scoped_ptr.h"
 #include "chrome/browser/chromeos/drive/drive_cache.h"
 #include "chrome/browser/chromeos/drive/drive_resource_metadata.h"
 #include "chrome/browser/google_apis/gdata_operations.h"
 
 namespace gdata {
 class DocumentEntry;
 }
 
 namespace drive {
 
 class DriveEntryProto;
 class DriveFileSystemObserver;
+class DriveResourceMetadata;
 
 typedef std::vector<DriveEntryProto> DriveEntryProtoVector;
 
 // Information about search result returned by Search Async callback.
 // This is data needed to create a file system entry that will be used by file
 // browser.
 struct SearchResultInfo {
   SearchResultInfo(const FilePath& in_path, bool in_is_directory)
       : path(in_path),
         is_directory(in_is_directory) {
   }
 
   FilePath path;
   bool is_directory;
 };
 
+// Metadata of DriveFileSystem. Used by DriveFileSystem::GetMetadata().
+struct DriveFileSystemMetadata {
+  DriveFileSystemMetadata() : largest_changestamp(0) {}
+  ~DriveFileSystemMetadata() {}
+
+  int64 largest_changestamp;
+};
+
 // Used to get files from the file system.
 typedef base::Callback<void(DriveFileError error,
                             const FilePath& file_path,
                             const std::string& mime_type,
                             DriveFileType file_type)> GetFileCallback;
 
 // Used to read a directory from the file system.
 // Similar to ReadDirectoryCallback but this one provides
 // |hide_hosted_documents|
 // If |error| is not DRIVE_FILE_OK, |entries| is set to NULL.
@@ skipping 289 matching lines @@
 
   // Updates the data associated with the file referenced by |resource_id| and
   // |md5|.  The data is copied from |file_content_path|.
   //
   // |callback| will be called on the UI thread upon completion of operation.
   virtual void UpdateEntryData(const std::string& resource_id,
                                const std::string& md5,
                                scoped_ptr<gdata::DocumentEntry> entry,
                                const FilePath& file_content_path,
                                const base::Closure& callback) = 0;
+
+  // Returns metadata of the file system.
+  virtual DriveFileSystemMetadata GetMetadata() const = 0;
 };
 
 }  // namespace drive
 
 #endif  // CHROME_BROWSER_CHROMEOS_DRIVE_DRIVE_FILE_SYSTEM_INTERFACE_H_