In the Win32 platform our setTitle() can properly assign a Unicode
utf-8 window title. Unfortunately our getTitle() will only read regular
8-bit character strings. This means that we can never compare what we
set to what we get. This patch updates getTitle() to use Unicode-aware
GetWindowTextLengthW and GetWindowTextW.

Bug report T88909 shows that the "Render" window could be created multiple times when in Chinese. This is because when creating a new temporary window we check to see if there are any temporary windows with the same title, and if so will use the same window. In this case we are comparing a utf-8 new title against current window titles that are being read as regular 8-bit chars. Therefore they never match and always create a new window.