Add definition for chrome.declarativeContent.ShowAction.

PiperOrigin-RevId: 562074531

Author: Closure Team

contrib/externs/chrome_extensions.js

@@ -12345,6 +12345,13 @@ chrome.declarativeContent.PageStateMatcherLiteral;
 chrome.declarativeContent.PageStateMatcher = function(literalValue) {};
 
 
+/**
+ * @constructor
+ * @see https://developer.chrome.com/extensions/declarativeContent#type-ShowAction
+ */
+chrome.declarativeContent.ShowAction = function() {};
+
+
 /**
  * @constructor
  * @see https://developer.chrome.com/extensions/declarativeContent#type-ShowPageAction