ChromeVox enabled for every WebDialog created by call to ShowWebDialog.

chrome/browser/ui/views/chrome_web_dialog_view.cc

 // 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.
 
+#include "chrome/browser/extensions/chrome_extension_web_contents_observer.h"
 #include "chrome/browser/ui/browser_dialogs.h"
 #include "chrome/browser/ui/webui/chrome_web_contents_handler.h"
 #include "ui/views/controls/webview/web_dialog_view.h"
 #include "ui/views/widget/widget.h"
 
 namespace chrome {
 
 // Declared in browser_dialogs.h so that others don't need to depend on our .h.
 gfx::NativeWindow ShowWebDialog(gfx::NativeWindow parent,
                                 content::BrowserContext* context,
                                 ui::WebDialogDelegate* delegate) {
   views::Widget* widget = NULL;
+  views::WebDialogView* view =
+      new views::WebDialogView(context, delegate, new ChromeWebContentsHandler);
   if (parent) {
-    widget = views::Widget::CreateWindowWithParent(
-        new views::WebDialogView(context,
-                                 delegate,
-                                 new ChromeWebContentsHandler),
-        parent);
+    widget = views::Widget::CreateWindowWithParent(view, parent);
   } else {
     // We shouldn't be called with a NULL parent, but sometimes are.
-    widget = views::Widget::CreateWindow(
-        new views::WebDialogView(context,
-                                 delegate,
-                                 new ChromeWebContentsHandler));
+    widget = views::Widget::CreateWindow(view);
   }
 
+  // Observer is needed for ChromeVox extension to send messages between content

[msw, 2014/04/28 18:32:45]

Are there security concerns with enabling extensions for our WebUI dialogs?
Could extensions modify dialog content that's presented as trusted Chrome UI?
I'm sure we have a solution for our chrome:// scheme WebUI pages, but I'm not
sure the same solution is in place for web dialog content. How does ChromeVox
fair on chrome://settings?

You should probably ping the security team, CC some webui/extensions/content
owners, and get c/b/ui/views owners review from ben or sky.

[dzhioev (left Google), 2014/04/28 19:15:53]

Creating ChromeExtensionWebContentsObserver makes possible communication between
injected code
and background page. But it doesn't make possible for any extension to inject
their code in the web
contents.

ChromeVox is an exception - it can inject its script into any web contents
including "chrome://*" pages.
(See here
https://code.google.com/p/chromium/codesearch#chromium/src/chrome/common/exte...
).
But if ChromeExtensionWebContentsObserver was not created for that contents,
injected code can't communicate with background script
and spoken feedback doesn't work.

Adding dmazzoni@ to confirm my words.

[dmazzoni, 2014/05/22 16:39:52]

Thanks for the ping.

Confirmed - just adding a ChromeExtensionWebContentsObserver doesn't make it any
easier for a random third-party extension to have access to this page, all it
would do is make it easier for them to send a message to their background page
if they did manage to inject their extension.

Also, if it helps, we have a plan underway to remove the need for injecting the
ChromeVox content script at all, but that's a couple of quarters away before we
could remove this code.

+  // and background scripts.
+  extensions::ChromeExtensionWebContentsObserver::CreateForWebContents(
+      view->web_contents());
+
   widget->Show();
   return widget->GetNativeWindow();
 }
 
 }  // namespace chrome