Public Sessions - prompt the user for pageCapture requests

chrome/browser/chromeos/extensions/public_session_permission_helper.h

Index: chrome/browser/chromeos/extensions/public_session_permission_helper.h
diff --git a/chrome/browser/chromeos/extensions/public_session_permission_helper.h b/chrome/browser/chromeos/extensions/public_session_permission_helper.h
new file mode 100644
index 0000000000000000000000000000000000000000..0da9203f6a640d22c66ac7ad8e4a78e4c37851d1
--- /dev/null
+++ b/chrome/browser/chromeos/extensions/public_session_permission_helper.h
@@ -0,0 +1,72 @@
+// Copyright 2017 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.
+
+#ifndef CHROME_BROWSER_CHROMEOS_EXTENSIONS_PUBLIC_SESSION_PERMISSION_HELPER_H_
+#define CHROME_BROWSER_CHROMEOS_EXTENSIONS_PUBLIC_SESSION_PERMISSION_HELPER_H_
+
+#include <map>
+#include <set>
+#include <vector>
+
+#include "base/callback_forward.h"
+#include "base/macros.h"
+#include "extensions/common/extension_id.h"
+#include "extensions/common/permissions/api_permission.h"
+
+namespace content {
+class WebContents;
+}
+
+namespace extensions {
+
+class Extension;
+
+namespace permission_helper {

[Devlin, 2017/01/23 22:59:48]

we probably don't need a namespace just for these classes.

[Ivan Šandrk, 2017/01/24 19:57:22]

Done.

+
+class PublicSessionPermissionHelperImpl;
+enum PermissionState {

[Devlin, 2017/01/23 22:59:48]

It looks like this might not be used at all?

[Ivan Šandrk, 2017/01/24 19:57:22]

Used in public_session_media_access_handler.cc

[Devlin, 2017/01/25 16:00:31]

Ah, that file didn't used to exist. :)

+  NOT_PROMPTED = 0,
+  SHOWN_PROMPT,
+  ALLOWED,
+  DENIED
+};
+using PermissionHelperSet = std::set<APIPermission::ID>;

[Devlin, 2017/01/23 22:59:48]

We have an APIPermissionSet; is there a reason we can't use that here?

[Ivan Šandrk, 2017/01/24 19:57:22]

ContainsAnyID accepts a set<APIPermission::ID> but not a APIPermissionSet.

PermissionIDSet would be really good if it could work with ContainsAnyID and if
it had a clean constructor from an initializer list (or something like this).
Are you fine with me making modifications to PermissionIDSet? :-)

[Devlin, 2017/01/25 16:00:31]

Grr... these weird sets are annoying (totally not related to this CL).  I don't
want to ask you to make yet-more-changes, since I've already been pretty picky
here. ;)

Let's move the typedef into private: part of the class so it doesn't pollute the
overall namespace, and put a note of why we have it.

[Ivan Šandrk, 2017/01/26 18:53:21]

Done.

+
+class PublicSessionPermissionHelper {
+ public:
+  static PublicSessionPermissionHelper& Instance();

[Devlin, 2017/01/23 22:59:48]

style forbids non-const refs being returned.

[Ivan Šandrk, 2017/01/24 19:57:22]

Can you link this? I wasn't able to find it in the style.

[Devlin, 2017/01/25 16:00:31]

Hmm... I've found
https://google.github.io/styleguide/cppguide.html#Reference_Arguments, which
requires it for parameters.  I've also found numerous places in the codebase
where it references that we don't allow them.  I wonder if a rule changed
recently, or if we're supposed to infer that reference arguments apply to return
values?

In either case, since I've failed to come up with a link, we can ignore this one
(I have no personal objections to it).

[Ivan Šandrk, 2017/01/26 18:53:21]

I think people have misunderstood that rule to mean "never use non-const refs
when functions are involved" :) Titus Winters talks about it here
https://goto.google.com/totw/87:

So, if non-const references are only forbidden as interface parameters, are
there still good uses for them? Of course. You may sometimes want to return a
non-const reference from a function.

+
+  // Sets up the prompt asking the user for additional permission(s), handles
+  // the result, caches it, and then runs either success_callback or
+  // failure_callback depending on all permissions being allowed.
+  // Supports handling multiple requests for the same permission(s). Only the
+  // first request causes the prompt to be shown, subsequent ones are just
+  // enqueued to be called when the permission(s) is resolved.
+  // Caller must ensure that web_contents is valid. requested_permissions may
+  // contain at most 2 elements. Must be called on UI thread.
+  // If finer resolving is needed, pass the same function in both callbacks and
+  // check the individual permissions by calling GetUserChoice inside your
+  // function.
+  void HandlePermissionRequest(const Extension* extension,
+                               PermissionHelperSet requested_permissions,
+                               content::WebContents* web_contents,
+                               const base::Closure& success_callback,
+                               const base::Closure& failure_callback);
+
+  PermissionState GetUserChoice(ExtensionId extension_id,

[Devlin, 2017/01/23 22:59:48]

Needed?

[Ivan Šandrk, 2017/01/24 19:57:22]

I'll upload also the changes to the other files so it becomes more apparent why
it's needed.

+                                APIPermission::ID permission_id);
+
+ private:
+  PublicSessionPermissionHelper();
+  ~PublicSessionPermissionHelper();
+
+  std::map<ExtensionId, PublicSessionPermissionHelperImpl> impl_;
+
+  DISALLOW_COPY_AND_ASSIGN(PublicSessionPermissionHelper);
+};
+
+}  // namespace permission_helper
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_CHROMEOS_EXTENSIONS_PUBLIC_SESSION_PERMISSION_HELPER_H_