RFR: 8280982: [Wayland] [XWayland] java.awt.Robot taking screenshots [v11]

[Alexander Zvegintsev]

> Modern Linux systems often come with [Wayland](https://wayland.freedesktop.org/) by default.
> This comes with some difficulties, and one of them is the inability to get screenshots from the system.
> This is because we now use the [X Window System API](https://en.wikipedia.org/wiki/X_Window_System) to capture screenshots and it cannot access data outside the [XWayland server](https://wayland.freedesktop.org/xserver.html) 
> 
> But this functionality is a very important part of automated testing.
> 
> 
> At the moment there are two obvious solutions to this problem, and both use [xdg-desktop-portal](https://github.com/flatpak/xdg-desktop-portal):
> 
> 1. [org.freedesktop.portal.Screenshot DBUS API](https://flatpak.github.io/xdg-desktop-portal/#gdbus-org.freedesktop.portal.Screenshot)
> It has several drawbacks though:
> + It saves a screenshot to disk, which must be read and deleted(may add some delays depending on the type of a disk drive).
> + There is no way to disable the visual "screen flash" after screenshot
> + It asks a user confirmation to save a screenshot. This confirmation can be saved on Gnome 43+. 
> Since we would like Ubuntu 22.04 LTS which comes with Gnome 42 this option is not acceptable for us because it would require user confirmation for each screenshot.
> But we still can consider this option as a fallback.
> 
> 
> 
> 2. [org.freedesktop.portal.ScreenCast](https://flatpak.github.io/xdg-desktop-portal/#gdbus-org.freedesktop.portal.ScreenCast)
> It typically used by applications that need to capture the contents of the user's screen or a specific window for the purpose of sharing, recording, or streaming.
> This might be a bit of overkill, but it avoids several of the problems mentioned in the Screenshot API.
> 
> + implementation is more complicated comparing to Screenshot API
> + no intermediate file, screenshot data can be obtained from memory
> + Permission to make screenshots can be stored with [`restore_token`](https://flatpak.github.io/xdg-desktop-portal/#gdbus-method-org-freedesktop-portal-ScreenCast.SelectSources)
> 
> 
> So this PR adds the ability to take screenshots using the ScreenCast API. This functionality is currently disabled by default.
> 
> This change also introduces some new behavior for the robot:
> A system window now appears asking for confirmation from the user to capture the screen.
> + The user can refuse the screen capture completely. In this case a security exception will be thrown.
> + The user can allow a screen capture for all screens or some of them. For screens witho...

Alexander Zvegintsev has updated the pull request incrementally with two additional commits since the last revision:

 - move screencast-tokens.properties to a new location
 - fix failure of javax/swing/reliability/HangDuringStaticInitialization.java in headless environment

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/13803/files
  - new: https://git.openjdk.org/jdk/pull/13803/files/63b34b9d..f5579309

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13803&range=10
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13803&range=09-10

  Stats: 4 lines in 1 file changed: 3 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/13803.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13803/head:pull/13803

PR: https://git.openjdk.org/jdk/pull/13803