[fsp] Remove length from the OnWriteFileOperation().

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 158 matching lines @@
     DOMString filePath;
     double length;
   };
 
   // Options for the <code>onWriteFileRequested()</code> event.
   dictionary WriteFileRequestedOptions {
     DOMString fileSystemId;
     long requestId;
     long openRequestId;
     double offset;
-    double length;
     ArrayBuffer data;
   };
 
   // Options for the <code>onAbortRequested()</code> event.
   dictionary AbortRequestedOptions {
     DOMString fileSystemId;
     long requestId;
     long operationRequestId;
   };
 
@@ skipping 172 matching lines @@
     // </code> must be called. Note, that callbacks of the aborted operation
     // should not be called, as they will be ignored. Despite calling <code>
     // errorCallback</code>, the request may be forcibly aborted. 
     [maxListeners=1, nodoc] static void onAbortRequested(
         AbortRequestedOptions options,
         ProviderSuccessCallback successCallback,
         ProviderErrorCallback errorCallback);
   };
 };