WinForms designer does not properly jump to code when double-clicking a control or event. #525

Not sure if this is a single bug, or multiple related bugs.

1. Create a new WinForms application and open the designer for MainForm.cs
2. Add a new button to the form and double-click it.
   Expected result: SD switches to the code editor and places the caret in the newly created event handler method.
   Actual result: SD switches to the code editor, but places the caret at (1,1).
3. Switch back to the designer, then double-click the button again.
   Expected result: SD switches to the code editor and places the caret in the existing event handler method.
   Actual result: SD does not switch to the code editor. However, on certain actions, such as moving the mouse outside the design surface, or selecting a different WinForms control, SD suddenly performs the switch.
   Repeating step 3 multiple times, it seems that the caret is placed correctly on every second attempt, and placed at (1,1) otherwise.

These problems also occur when creating an event handler from the property pad. In that case, moving the mouse outside of the property pad will suddenly cause SD to switch to the source code.

I possible cause might be that the WinForms Application.Idle event only fires when the mouse is over a WPF control. We had trouble with WinForms Application.Idle not firing earlier (in SD 4.x), see http://stackoverflow.com/questions/2344398/application-idle-event-not-firing-in-wpf-application