Find an existing terminal if one exists to position settings

Bug: 1056983
Change-Id: Ic0671f0c06a9390346537343a94a28b75adbca63
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2096605
Auto-Submit: Joel Hockey <joelhockey@chromium.org>
Commit-Queue: Alan Cutter <alancutter@chromium.org>
Reviewed-by: Alan Cutter <alancutter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#749511}

chrome/browser/chromeos/crostini/crostini_terminal.cc

@@ -136,6 +136,10 @@ void LaunchTerminalSettings(Profile* profile, Browser* terminal) {
   params->disposition = WindowOpenDisposition::NEW_POPUP;
   // If |terminal| is not set, we open the settings window with the
   // default bounds and then resize it later.
+  if (!terminal) {
+    terminal = web_app::FindSystemWebAppBrowser(
+        profile, web_app::SystemAppType::TERMINAL);
+  }
   if (terminal) {
     const gfx::Rect& bounds = terminal->window()->GetBounds();
     params->override_bounds.set_origin(