Explicitly refit overlay for cherry pick dialog

Overlay refit() is called when cherry pick dialog is opened but after
selecting the cherry pick topic option, overlay is not refitted
and hence results in taking more height than available which end
up hiding the confirm button.

This solution is also not ideal since calling refit everytime
the user selects a different option results in the dialog changing
it's position to fit to the screen size. However, it allows the
confirm button to always be visible and it's unlikely users will
switch between the options many times.

Change-Id: Ifd2906a4e23fb87d85149e3cde4a1020e1ab11c6
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog.ts b/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog.ts
index 225e3e9..ebcabbf 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog.ts
+++ b/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog.ts
@@ -38,6 +38,7 @@
 import {AutocompleteSuggestion} from '../../shared/gr-autocomplete/gr-autocomplete';
 import {HttpMethod, ChangeStatus} from '../../../constants/constants';
 import {dom, EventApi} from '@polymer/polymer/lib/legacy/polymer.dom';
+import {fireEvent} from '../../../utils/event-util';
 
 const SUGGESTIONS_LIMIT = 15;
 const CHANGE_SUBJECT_LIMIT = 50;
@@ -264,10 +265,12 @@
 
   _handlecherryPickSingleChangeClicked() {
     this._cherryPickType = CherryPickType.SINGLE_CHANGE;
+    fireEvent(this, 'iron-resize');
   }
 
   _handlecherryPickTopicClicked() {
     this._cherryPickType = CherryPickType.TOPIC;
+    fireEvent(this, 'iron-resize');
   }
 
   @observe('changeStatus', 'commitNum', 'commitMessage')