[fsp] Add an option for mounting in R/W mode.

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 39 matching lines @@
     [instanceOf=Date] object modificationTime;
 
     // Mime type for the entry.
     DOMString? mimeType; 
   };
 
   // Options for the <code>mount()</code> method.
   dictionary MountOptions {
     DOMString fileSystemId;
     DOMString displayName;
+    [nodoc] boolean? writable;
   };
 
   // Options for the <code>unmount()</code> method.
   dictionary UnmountOptions {
     DOMString fileSystemId;
   };
 
   // Options for the <code>onUnmountRequested()</code> event.
   dictionary UnmountRequestedOptions {
     DOMString fileSystemId;
@@ skipping 176 matching lines @@
     // Raised when deleting an entry is requested. If <code>recursive</code> is
     // true, and the entry is a directory, then all of the entries inside
     // must be recursively deleted as well.
     [maxListeners=1, nodoc] static void onDeleteEntryRequested(
         DeleteEntryRequestedOptions options,
         ProviderSuccessCallback successCallback,
         ProviderErrorCallback errorCallback);
   };
 };