[fsp] Add support for reading directories.

chrome/common/extensions/api/file_system_provider.idl

 // Copyright 2013 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.
 
 // Use the <code>chrome.fileSystemProvider</code> API to create file systems,
 // that can be accessible from the file manager on Chrome OS.
 [platforms=("chromeos"),
  implemented_in="chrome/browser/chromeos/extensions/file_system_provider/file_system_provider_api.h"]
 namespace fileSystemProvider {
   // Error codes used by providing extensions in response to requests. For
@@ skipping 51 matching lines @@
 
   // Callback to be called by the providing extension in case of an error.
   callback ProviderErrorCallback = void(ProviderError error);
 
   // Callback to handle an error raised from the browser.
   [nocompile] callback ErrorCallback = void([instanceOf=DOMError] object error);
 
   // Success callback for the <code>onGetMetadataRequested</code> event.
   callback MetadataCallback = void(EntryMetadata metadata);
 
+  // Success callback for the <code>onDirectoryRequested</code> event. If more
+  // entries will be returned, then <code>hasNext</code> must be true, and it
+  // has to be called again with additional entries. If no more entries are
+  // available, then <code>hasNext</code> must be set to false.
+  callback EntriesCallback = void(ResourceEntry[] entries, bool hasNext);
+
   interface Functions {
     // Mounts a file system with the given <code>displayName</code>.
     // <code>displayName</code> will be shown in the left panel of
     // Files.app. <code>displayName</code> can contain any characters
     // including '/', but cannot be an empty string. <code>displayName</code>
     // should be descriptive but doesn't have to be unique. Duplicate display
     // names are uniquified by adding suffix like "(1)" in the Files.app UI.
     static void mount(DOMString displayName,
                       MountCallback successCallback,
                       [nocompile] ErrorCallback errorCallback);
@@ skipping 22 matching lines @@
 
     // Raised when metadata of a file or a directory at <code>entryPath</code>
     // is requested. The metadata should be returned with the <code>
     // successCallback</code> call. In case of an error, <code>errorCallback
     // </code> must be called.
     [maxListeners=1] static void onGetMetadataRequested(
         long fileSystemId,
         DOMString entryPath,
         MetadataCallback successCallback,
         ErrorCallback errorCallback);
+
+    // Raised when contents of a directory at <code>directoryPath</code> is

[benwells, 2014/05/05 01:07:24]

Grammar nit: should be "Raised when /the/ contents of a directory at ... /are/
requested. /The/ results should be returned..."

[mtomasz, 2014/05/07 04:57:30]

Done.

+    // requested. Results should be returned in chunks by calling the <code>
+    // successCallback</code> several times. In case of an error, <code>
+    // errorCallback</code> must be called.
+    [maxListeners=1] static void onReadDirectoryRequested(
+        long fileSystemId,
+        DOMString directoryPath,
+        EntriesCallback successCallback,
+        ErrorCallback errorCallback);
   };
 };