Add max-rows to the PG revert dialog

Bug: Issue 4740
Change-Id: I9484fb92eba6df9547a003ab789bb22a98cde2af
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.html b/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.html
index 979a06a..b668d06 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.html
+++ b/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.html
@@ -55,6 +55,7 @@
         </label>
         <iron-autogrow-textarea
             id="messageInput"
+            max-rows="15"
             class="message"
             bind-value="{{message}}"></iron-autogrow-textarea>
       </div>