[Viewer] Set the current slide first before attaching the fBackendType to fWindow.

If call attach() first, Viewer::onBackendCreated() calls Window::show().
When WM_PAINT occurs, Viewer::drawSlide() is called, where a crash occurs using an uninitialized fCurrentSlide.

Bug: skia:https://bugs.chromium.org/p/skia/issues/detail?id=8792
Change-Id: I22ba6479052cb66e08d8bc2a94539473e899b604
Reviewed-on: https://skia-review.googlesource.com/c/195240
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
diff --git a/AUTHORS b/AUTHORS
index ff6fc6c..a66487d 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -27,6 +27,7 @@
 Ion Rosca <rosca@adobe.com>
 Jacek Caban <cjacek@gmail.com>
 Jeff Muizelaar <jmuizelaar@mozilla.com>
+Jongdeok Kim <jongdeok.kim@navercorp.com>
 Lee Salzman <lsalzman@mozilla.com>
 Marcin Kazmierczak <mar.kazmierczak@gmail.com>
 Matthew Leibowitz <mattleibow@live.com>