[fsp] First part of support for reading files.

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 57 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
+  // Success callback for the <code>onReadDirectoryRequested</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);
 
+  // Success callback for the <code>onReadFileRequested</code> event. If more
+  // data will be returned, then <code>hasNext</code> must be true, and it
+  // has to be called again with additional entries. If no more data is
+  // available, then <code>hasNext</code> must be set to false.
+  callback FileDataCallback = void(DOMString data, 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 51 matching lines @@
         ProviderSuccessCallback successCallback,
         ProviderErrorCallback errorCallback);
 
     // Raised when opening a file previously opened with <code>openRequestId
     // </code> is requested to be closed.
     [maxListeners=1] static void onCloseFileRequested(
         long fileSystemId,
         long openRequestId,
         ProviderSuccessCallback successCallback,
         ProviderErrorCallback errorCallback);
+
+    // Raised when contents of a file opened previously with <code>openRequestId
+    // </code>. The results should be returned in chunks by calling <code>
+    // successCallback</code> several times. In case of an error, <code>
+    // errorCallback</code> must be called.
+    [maxListeners=1] static void onReadFileRequested(
+        long fileSystemId,
+        long openRequestId,
+        double offset,
+        double length,
+        FileDataCallback successCallback,
+        ProviderErrorCallback errorCallback);
   };
 };