[Extensions Page] Add a listener on extension list for "hasExtensions" changing

Add a listener on the ExtensionList object for when the count of extensions
moves from 0 to 1, or from 1 to 0 - i.e., when we should show or hide the
list.

BUG=480110

Review URL: https://codereview.chromium.org/1105683003

Cr-Commit-Position: refs/heads/master@{#327201}

chrome/browser/extensions/api/developer_private/developer_private_api.cc

@@ -226,12 +226,10 @@ void DeveloperPrivateEventRouter::OnExtensionUnloaded(
   BroadcastItemStateChanged(developer::EVENT_TYPE_UNLOADED, extension->id());
 }
 
-void DeveloperPrivateEventRouter::OnExtensionWillBeInstalled(
+void DeveloperPrivateEventRouter::OnExtensionInstalled(
     content::BrowserContext* browser_context,
     const Extension* extension,
-    bool is_update,
-    bool from_ephemeral,
-    const std::string& old_name) {
+    bool is_update) {
   DCHECK(profile_->IsSameProfile(Profile::FromBrowserContext(browser_context)));
   BroadcastItemStateChanged(developer::EVENT_TYPE_INSTALLED, extension->id());
 }

chrome/browser/extensions/api/developer_private/developer_private_api.h

@@ -68,11 +68,9 @@ class DeveloperPrivateEventRouter : public ExtensionRegistryObserver,
   void OnExtensionUnloaded(content::BrowserContext* browser_context,
                            const Extension* extension,
                            UnloadedExtensionInfo::Reason reason) override;
-  void OnExtensionWillBeInstalled(content::BrowserContext* browser_context,
-                                  const Extension* extension,
-                                  bool is_update,
-                                  bool from_ephemeral,
-                                  const std::string& old_name) override;
+  void OnExtensionInstalled(content::BrowserContext* browser_context,
+                            const Extension* extension,
+                            bool is_update) override;
   void OnExtensionUninstalled(content::BrowserContext* browser_context,
                               const Extension* extension,
                               extensions::UninstallReason reason) override;

chrome/browser/resources/extensions/extension_list.js

@@ -162,15 +162,26 @@ cr.define('extensions', function() {
            compare(a.id, b.id);
   }
 
+  /** @interface */
+  function ExtensionListDelegate() {}
+
+  ExtensionListDelegate.prototype = {
+    /**
+     * Called when the number of extensions in the list has changed.
+     */
+    onExtensionCountChanged: assertNotReached,
+  };
+
   /**
    * Creates a new list of extensions.
+   * @param {extensions.ExtensionListDelegate} delegate
    * @constructor
    * @extends {HTMLDivElement}
    */
-  function ExtensionList() {
+  function ExtensionList(delegate) {
     var div = document.createElement('div');
     div.__proto__ = ExtensionList.prototype;
-    div.initialize();
+    div.initialize(delegate);
     return div;
   }
 
@@ -230,11 +241,15 @@ cr.define('extensions', function() {
 
     /**
      * Initializes the list.
+     * @param {!extensions.ExtensionListDelegate} delegate
      */
-    initialize: function() {
+    initialize: function(delegate) {
       /** @private {!Array<ExtensionInfo>} */
       this.extensions_ = [];
 
+      /** @private {!extensions.ExtensionListDelegate} */
+      this.delegate_ = delegate;
+
       /**
        * |loadFinished| should be used for testing purposes and will be
        * fulfilled when this list has finished loading the first time.
@@ -260,12 +275,19 @@ cr.define('extensions', function() {
               this.updateExtension_(eventData.extensionInfo);
             break;
           case EventType.UNINSTALLED:
+            var index = this.getIndexOfExtension_(eventData.item_id);
+            this.extensions_.splice(index, 1);
             var childNode = $(eventData.item_id);
             childNode.parentNode.removeChild(childNode);
             break;
           default:
             assertNotReached();
         }
+
+        if (eventData.event_type == EventType.INSTALLED ||
+            eventData.event_type == EventType.UNINSTALLED) {
+          this.delegate_.onExtensionCountChanged();
+        }
       }.bind(this));
     },
 
@@ -334,6 +356,19 @@ cr.define('extensions', function() {
       return this.extensions_.length;
     },
 
+    /**
+     * @param {string} id The id of the extension.
+     * @return {number} The index of the extension with the given id.
+     * @private
+     */
+    getIndexOfExtension_: function(id) {
+      for (var i = 0; i < this.extensions_.length; ++i) {
+        if (this.extensions_[i].id == id)
+          return i;
+      }
+      return -1;
+    },
+
     getIdQueryParam_: function() {
       return parseQueryParams(document.location)['id'];
     },
@@ -1063,13 +1098,7 @@ cr.define('extensions', function() {
      * @private
      */
     updateExtension_: function(extension) {
-      var currIndex = -1;
-      for (var i = 0; i < this.extensions_.length; ++i) {
-        if (this.extensions_[i].id == extension.id) {
-          currIndex = i;
-          break;
-        }
-      }
+      var currIndex = this.getIndexOfExtension_(extension.id);
       if (currIndex != -1) {
         // If there is a current version of the extension, update it with the
         // new version.
@@ -1093,6 +1122,7 @@ cr.define('extensions', function() {
   };
 
   return {
-    ExtensionList: ExtensionList
+    ExtensionList: ExtensionList,
+    ExtensionListDelegate: ExtensionListDelegate
   };
 });

chrome/browser/resources/extensions/extensions.js

@@ -98,6 +98,8 @@ cr.define('extensions', function() {
   /**
    * ExtensionSettings class
    * @class
+   * @constructor
+   * @implements {extensions.ExtensionListDelegate}
    */
   function ExtensionSettings() {}
 
@@ -133,7 +135,7 @@ cr.define('extensions', function() {
       // Set the title.
       uber.setTitle(loadTimeData.getString('extensionSettings'));
 
-      var extensionList = new ExtensionList();
+      var extensionList = new ExtensionList(this);
       extensionList.id = 'extension-settings-list';
       var wrapper = $('extension-list-wrapper');
       wrapper.insertBefore(extensionList, wrapper.firstChild);
@@ -274,10 +276,7 @@ cr.define('extensions', function() {
           document.documentElement.classList.remove('loading');
         }, 0);
 
-        /** @const */
-        var hasExtensions = extensionList.getNumExtensions() != 0;
-        $('no-extensions').hidden = hasExtensions;
-        $('extension-list-wrapper').hidden = !hasExtensions;
+        this.onExtensionCountChanged();
       }.bind(this));
     },
 
@@ -293,10 +292,9 @@ cr.define('extensions', function() {
 
     /**
      * Shows the Extension Commands configuration UI.
-     * @param {Event} e Change event.
      * @private
      */
-    showExtensionCommandsConfigUi_: function(e) {
+    showExtensionCommandsConfigUi_: function() {
       ExtensionSettings.showOverlay($('extension-commands-overlay'));
       chrome.send('metricsHandler:recordAction',
                   ['Options_ExtensionCommands']);
@@ -347,8 +345,20 @@ cr.define('extensions', function() {
             buttons.offsetHeight + 'px';
       }.bind(this));
     },
+
+    /** @override */
+    onExtensionCountChanged: function() {
+      /** @const */
+      var hasExtensions = $('extension-settings-list').getNumExtensions() != 0;
+      $('no-extensions').hidden = hasExtensions;
+      $('extension-list-wrapper').hidden = !hasExtensions;
+    },
   };
 
+  /**
+   * Called by the WebUI when something has changed and the extensions UI needs
+   * to be updated.
+   */
   ExtensionSettings.onExtensionsChanged = function() {
     ExtensionSettings.getInstance().update_();
   };