Generate synthetic mouse button up if the mouse has left the window and the button is raised

app/streaming/input/input.h

@@ -69,6 +69,8 @@ public:
 
     void raiseAllKeys();
 
+    void notifyMouseLeave();
+
     void notifyFocusLost();
 
     bool isCaptureActive();
@@ -124,6 +126,7 @@ private:
     int m_StreamHeight;
     bool m_AbsoluteMouseMode;
     bool m_AbsoluteTouchMode;
+    Uint32 m_PendingMouseLeaveButtonUp;
 
     SDL_TouchFingerEvent m_TouchDownEvent[MAX_FINGERS];
     SDL_TimerID m_LeftButtonReleaseTimer;