ozone: scenic: Add missing Present() call to UpdateSize()

When using vulkan, there is no per-frame Present() call to the window's
scenic session. We need to make sure to call present after a size update
to commit the new size.

Bug: 861853
Test: run_content_shell --ozone-platform=scenic --disable-gpu --enable-vulkan
Change-Id: I7d2788ae6ff641908a10a02d837bea223af6a1ca
Reviewed-on: https://chromium-review.googlesource.com/c/1330291
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607330}

ui/ozone/platform/scenic/scenic_window.cc

@@ -200,6 +200,11 @@ void ScenicWindow::UpdateSize() {
   shape_node_.SetTranslation(size_dips_.width() / 2.0,
                              size_dips_.height() / 2.0, 0.f);
 
+  // This is necessary when using vulkan because ImagePipes are presented
+  // separately and we need to make sure our sizes change is committed.
+  scenic_session_.Present(
+      /*presentation_time=*/0, [](fuchsia::images::PresentationInfo info) {});
+
   delegate_->OnBoundsChanged(size_rect);
 }