Focus into textbox when abandon issue modal opens

Previously, when you click on the "abandon change button", and the
pop-up opened, the cursor was not focused on the textarea. This change
fixes that.

Bug: Issue 4214

Change-Id: Ie01f009ef56884ca87723be0fc25669c96ee882d
diff --git a/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.js b/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.js
index 8deab6b..f91816b 100644
--- a/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.js
+++ b/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.js
@@ -397,7 +397,11 @@
 
     _showActionDialog: function(dialog) {
       dialog.hidden = false;
-      this.$.overlay.open();
+      this.$.overlay.open().then(function() {
+        if (dialog.resetFocus) {
+          dialog.resetFocus();
+        }
+      });
     },
 
     _handleResponse: function(action, response) {
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-abandon-dialog/gr-confirm-abandon-dialog.js b/polygerrit-ui/app/elements/change/gr-confirm-abandon-dialog/gr-confirm-abandon-dialog.js
index 0ce1cbb..e47f14f 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-abandon-dialog/gr-confirm-abandon-dialog.js
+++ b/polygerrit-ui/app/elements/change/gr-confirm-abandon-dialog/gr-confirm-abandon-dialog.js
@@ -33,6 +33,10 @@
       message: String,
     },
 
+    resetFocus: function() {
+      this.$.messageInput.textarea.focus();
+    },
+
     _handleConfirmTap: function(e) {
       e.preventDefault();
       this.fire('confirm', {reason: this.message}, {bubbles: false});