Add custom action support

third_party/closure_compiler/externs/automation.js

Index: third_party/closure_compiler/externs/automation.js
diff --git a/third_party/closure_compiler/externs/automation.js b/third_party/closure_compiler/externs/automation.js
index 6bcb195c65ea05b1e489cea17030957d412a2ed2..b06a678e861c8b187b68197d3393d7ec7db9b8e2 100644
--- a/third_party/closure_compiler/externs/automation.js
+++ b/third_party/closure_compiler/externs/automation.js
@@ -366,6 +366,15 @@ chrome.automation.TreeChangeObserverFilter = {
   ALL_TREE_CHANGES: 'allTreeChanges',
 };
 
+/**
+ * @typedef {{
+ *   id: number,
+ *   description: string
+ * }}
+ * @see https://developer.chrome.com/extensions/automation#type-CustomAction
+ */
+chrome.automation.CustomAction;
+
 /**
  * @constructor
  * @private
@@ -531,6 +540,13 @@ chrome.automation.AutomationNode.prototype.activeDescendant;
  */
 chrome.automation.AutomationNode.prototype.inPageLinkTarget;
 
+/**
+ * An array of custom actions.
+ * @type {(!Array<!chrome.automation.CustomAction>|undefined)}
+ * @see https://developer.chrome.com/extensions/automation#type-customActions
+ */
+chrome.automation.AutomationNode.prototype.customActions;
+
 /**
  * The URL that this link will navigate to.
  * @type {(string|undefined)}
@@ -1076,6 +1092,13 @@ chrome.automation.AutomationNode.prototype.hitTest = function(x, y, eventToFire)
  */
 chrome.automation.AutomationNode.prototype.makeVisible = function() {};
 
+/**
+ * Performs custom action.
+ * @param {number} customActionId
+ * @see https://developer.chrome.com/extensions/automation#method-performCustomAction
+ */
+chrome.automation.AutomationNode.prototype.performCustomAction = function(customActionId) {};
+
 /**
  * Sets selection within a text field.
  * @param {number} startIndex