Plumb file system permission into WebviewGuest.

chrome/renderer/resources/extensions/web_view.js

 // 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.
 
 // This module implements Webview (<webview>) as a custom element that wraps a
 // BrowserPlugin object element. The object element is hidden within
 // the shadow DOM of the Webview element.
 
 var DocumentNatives = requireNative('document_natives');
 var EventBindings = require('event_bindings');
@@ skipping 669 matching lines @@
     },
     enumerable: true
   });
 };
 
 /**
  * @private
  */
 WebViewInternal.prototype.getPermissionTypes = function() {
   var permissions =
-      ['media', 'geolocation', 'pointerLock', 'download', 'loadplugin'];
+      ['media',
+      'geolocation',
+      'pointerLock',
+      'download',
+      'loadplugin',
+      'filesystem'];

[not at google - send to devlin, 2014/06/05 16:57:04]

what does it mean for a webview to have the 'filesystem' permission?

[Xi Han, 2014/06/05 16:59:59]

From my understanding, it means the embedder can change the default permission
of file system access request from a guest, by explicitly allow or deny.

[not at google - send to devlin, 2014/06/05 17:03:17]

what kind of file system access? like access outside the sandbox? this isn't
related to chrome.fileSystem, right..?

[Xi Han, 2014/06/05 17:09:37]

It is html file system access, starting from window.requestFileSystem(..). No,
this isn't related to chrome.filesystem.

[not at google - send to devlin, 2014/06/05 17:12:50]

Ok cool.

I'm all for explicitly enabling features of webviews, but why is access to the
sandboxed file system prevented? seems pretty harmless.

[Xi Han, 2014/06/05 17:24:00]

Honestly, I don't know exactly why, but maybe because there are some cases that
the embedder don't want the guest to access local file systems, such as create a
new file, or delete a file.

[not at google - send to devlin, 2014/06/05 17:30:39]

That would make sense, but I thought requestFileSystem was for the sandboxed
file system and not related to <input type=file> or whatever (i.e.
out-of-sandbox file system).

and there's nothing dangerous about sandboxed file system access.

[Xi Han, 2014/06/05 17:45:07]

The guest can request both "Temporary" or "Persistent" file system access, maybe
the "persistent" access sometime is considered not safe. This is just from my
guess, and maybe we just want to implement this permission as the same way as
other permissions. 

   return permissions.concat(this.maybeGetExperimentalPermissions());
 };
 
 /**
  * @private
  */
 WebViewInternal.prototype.handleDialogEvent =
     function(event, webViewEvent) {
   var showWarningMessage = function(dialogType) {
     var VOWELS = ['a', 'e', 'i', 'o', 'u'];
@@ skipping 584 matching lines @@
 
 /**
  * Implemented when the experimental API is available.
  * @private
  */
 WebViewInternal.prototype.setupExperimentalContextMenus_ = function() {};
 
 exports.WebView = WebView;
 exports.WebViewInternal = WebViewInternal;
 exports.CreateEvent = CreateEvent;