Try to watch local variable in watchwindow-DND, too.

Fix codepath overlooked in
6886e485de by introducing
a WatchHandler::watchVariable().

Task-number: QTCREATORBUG-8120
Change-Id: Ibab2619754e0006f3c81810a6bfdf758261c169e
Reviewed-by: hjk <qthjk@ovi.com>

src/plugins/debugger/watchwindow.cpp

@@ -553,7 +553,7 @@ void WatchTreeView::dropEvent(QDropEvent *ev)
         QString data = ev->mimeData()->text();
         foreach (const QChar c, data)
             exp.append(c.isPrint() ? c : QChar(QLatin1Char(' ')));
-        watchExpression(exp);
+        currentEngine()->watchHandler()->watchVariable(exp);
         //ev->acceptProposedAction();
         ev->setDropAction(Qt::CopyAction);
         ev->accept();