Plumb file system permission into WebviewGuest.

chrome/renderer/resources/extensions/web_view.js

Index: chrome/renderer/resources/extensions/web_view.js
diff --git a/chrome/renderer/resources/extensions/web_view.js b/chrome/renderer/resources/extensions/web_view.js
index f0578f7ae76c0d5be08fe63fa17a66c46c24723f..079ff10613b007b2dd431818c490fcd0260b05d8 100644
--- a/chrome/renderer/resources/extensions/web_view.js
+++ b/chrome/renderer/resources/extensions/web_view.js
@@ -687,7 +687,12 @@ WebViewInternal.prototype.setupEventProperty = function(eventName) {
  */
 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());
 };