All file dialogs irrespective of source, platform and runtime will now be
routed through CefFileDialogManager and trigger CefDialogHandler callbacks
(see issue #3293).
Adds Chrome runtime support for CefBrowserHost::RunFileDialog and
CefDialogHandler callbacks.
Adds Alloy runtime support for internal GTK file and print dialogs on Linux
subject to the following limitations:
1. Internal GTK implementation:
- Cannot be used with multi-threaded-message-loop because Chromium's
internal GTK implementation is not thread-safe (does not use GDK threads).
- Dialogs will not be modal to application windows when used with off-screen
rendering due to lack of access to the client's top-level GtkWindow.
2. Cefclient CefDialogHandler implementation:
- Cannot be used with Views because it requires a top-level GtkWindow.
Due to the above limitations no dialog implementation is currently provided for
Views + multi-threaded-message-loop on Linux. In cases where both
implementations are supported the cefclient version is now behind an optional
`--use-client-dialogs` command-line flag.
Expressly forbids multiple simultaneous file dialogs with the internal platform
implementation which uses modal dialogs. CefDialogHandler will still be notified
and can optionally handle each request without a modal dialog (see issue #3154).
Removes some RunFileDialog parameters that are not supported by the Chrome file
dialog implementation (selected_accept_filter parameter, cef_file_dialog_mode_t
overwrite/read-only flags).
