Clip the screen capture area to the desktop for ARC.

This clips the requested screen capture area to the desktop window for
ArcScreenCaptureSession. AuraDesktopCapturer already does this.

Bug: b/118675936
Test: cts passes
Change-Id: I3795d21bf34f05e7f71e46f3fcc8ff2e50cec506
Reviewed-on: https://chromium-review.googlesource.com/c/1316985Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Commit-Queue: Eliot Courtney <edcourtney@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605572}

chrome/browser/chromeos/arc/screen_capture/arc_screen_capture_session.cc

@@ -361,6 +361,8 @@ void ArcScreenCaptureSession::OnAnimationStep(base::TimeTicks timestamp) {
           viz::CopyOutputRequest::ResultFormat::RGBA_TEXTURE,
           base::BindOnce(&ArcScreenCaptureSession::OnDesktopCaptured,
                          weak_ptr_factory_.GetWeakPtr()));
+  // Clip the requested area to the desktop area. See b/118675936.
+  request->set_area(gfx::Rect(desktop_window_->bounds().size()));
   layer->RequestCopyOfOutput(std::move(request));
 }