The dispatch function of FindbarDispatcher class is called when
Ctrl+f is pressed. This function makes Toolbar visible and takes
focus to TextField. So expand this function to insert the selected
text to TextField at the same time. With dynamic_cast convert
Window pointer, which point to the TextField and call TextField's new
function: SetTextToSelected_Impl(), which makes the mentioned
insertion.
Plus make a little cleanup. Replace one string, which is defined by
a macro.

Change-Id: I2a8a3b10a016f5b28ea58fa3e63a3f31c9a816bf