Revert of Revert "Typecheck JS files for chrome://extensions"

chrome/browser/resources/extensions/extensions.js

Index: chrome/browser/resources/extensions/extensions.js
diff --git a/chrome/browser/resources/extensions/extensions.js b/chrome/browser/resources/extensions/extensions.js
index fa8d7f02ddc0c11cfdd3664505d1ed3f52cf1ffa..3b929f7115f7dc7392ea5030e166c08a732aa6c2 100644
--- a/chrome/browser/resources/extensions/extensions.js
+++ b/chrome/browser/resources/extensions/extensions.js
@@ -5,16 +5,29 @@
 <include src="../uber/uber_utils.js">
 <include src="extension_code.js">
 <include src="extension_commands_overlay.js">
+<include src="extension_error_overlay.js">
 <include src="extension_focus_manager.js">
 <include src="extension_list.js">
 <include src="pack_extension_overlay.js">
-<include src="extension_error_overlay.js">
 <include src="extension_loader.js">
 <include src="extension_options_overlay.js">
 
 <if expr="chromeos">
 <include src="chromeos/kiosk_apps.js">
 </if>
+
+/**
+ * The type of the extension data object. The definition is based on
+ * chrome/browser/ui/webui/extensions/extension_settings_handler.cc:
+ *     ExtensionSettingsHandler::HandleRequestExtensionsData()
+ * @typedef {{developerMode: boolean,
+ *            extensions: Array,
+ *            incognitoAvailable: boolean,
+ *            loadUnpackedDisabled: boolean,
+ *            profileIsSupervised: boolean,
+ *            promoteAppsDevTools: boolean}}
+ */
+var ExtensionDataResponse;
 
 // Used for observing function of the backend datasource for this page by
 // tests.
@@ -259,7 +272,7 @@
       } else {
         $('extension-settings').classList.remove('dev-mode');
       }
-      window.setTimeout(this.updatePromoVisibility_.bind(this));
+      window.setTimeout(this.updatePromoVisibility_.bind(this), 0);
 
       chrome.send('extensionSettingsToggleDeveloperMode');
     },
@@ -280,6 +293,7 @@
   /**
    * Called by the dom_ui_ to re-populate the page with data representing
    * the current state of installed extensions.
+   * @param {ExtensionDataResponse} extensionsData
    */
   ExtensionSettings.returnExtensionsData = function(extensionsData) {
     // We can get called many times in short order, thus we need to
@@ -403,7 +417,7 @@
       pages[i].setAttribute('aria-hidden', node ? 'true' : 'false');
     }
 
-    overlay.hidden = !node;
+    $('overlay').hidden = !node;
     uber.invokeMethodOnParent(node ? 'beginInterceptingEvents' :
                                      'stopInterceptingEvents');
   };