Revert "Revert "Merge remote-tracking branch 'origin/4.15'""

This reverts commit f0a86d4510.

Reverting a merge doesn't "undo" it - the changes would be lost
forever even with subsequent merges.
So we need to revert the revert to get the changes.

Change-Id: I65928f876f4dc886561bed17c4b2aa42b388c1e3
Reviewed-by: Marco Bubke <marco.bubke@qt.io>

src/plugins/texteditor/codeassist/functionhintproposalwidget.h

@@ -52,6 +52,8 @@ public:
     void updateProposal(const QString &prefix) override;
     void closeProposal() override;
 
+    bool proposalIsVisible() const override;
+
 protected:
     bool eventFilter(QObject *o, QEvent *e) override;