Bug 1234317 - Update mLastSizeMode when window size mode changes within Windows widget, avoids a window focus problem on Windows 10 with theme changes. r=jimm

MozReview-Commit-ID: FFpH8iZbxXK

--HG--
extra : rebase_source : 6d092566a4f20c07f2b8944c6a0e9e683dc39663

widget/windows/nsWindow.cpp

@@ -6262,6 +6262,8 @@ void nsWindow::OnWindowPosChanged(WINDOWPOS* wp)
     if (mLastSizeMode != nsSizeMode_Normal && mSizeMode == nsSizeMode_Normal)
       DispatchFocusToTopLevelWindow(true);
 
+    mLastSizeMode = mSizeMode;
+
     // Skip window size change events below on minimization.
     if (mSizeMode == nsSizeMode_Minimized)
       return;