Pass no-cancel-on-outside-click to reply overlay

Bug: Issue 3869
Change-Id: Ie2d82d8800075e737eda8e684162cd66cd242e1d
diff --git a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.html b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.html
index e3f7fd2..46292e4 100644
--- a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.html
+++ b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.html
@@ -312,6 +312,7 @@
           on-close="_handleDownloadDialogClose"></gr-download-dialog>
     </gr-overlay>
     <gr-overlay id="replyOverlay"
+        no-cancel-on-outside-click
         on-iron-overlay-opened="_handleReplyOverlayOpen"
         with-backdrop>
       <gr-reply-dialog id="replyDialog"