Add a new App launcher promo to the apps page / NTP.

chrome/browser/resources/ntp4/page_list_view.js

Index: chrome/browser/resources/ntp4/page_list_view.js
diff --git a/chrome/browser/resources/ntp4/page_list_view.js b/chrome/browser/resources/ntp4/page_list_view.js
index 8fd59409b26dc5240ede0e66b27fc3daaff9f487..5c8a7bade0ee0c3de01f88535771bb873f5b7ce5 100644
--- a/chrome/browser/resources/ntp4/page_list_view.js
+++ b/chrome/browser/resources/ntp4/page_list_view.js
@@ -412,6 +412,9 @@ cr.define('ntp', function() {
         this.appsLoaded_ = true;
         cr.dispatchSimpleEvent(document, 'sectionready', true, true);
       }
+      $('app-launcher-promo').hidden =
+        !loadTimeData.getBoolean('showAppLauncherPromo') ||
+        this.shownPage != loadTimeData.getInteger('apps_page_id');
     },
 
     /**
@@ -475,6 +478,15 @@ cr.define('ntp', function() {
     },
 
     /**
+     * Callback invoked by chrome whenever the app launcher promo pref changes.
+     * @param {bool} show Identifies if we should show or hide the promo.

[Dan Beam, 2013/03/21 15:45:14]

{boolean}

[MAD, 2013/03/21 16:47:47]

Done.

+     */
+    appLauncherPromoPrefChangeCallback: function(show) {
+      $('app-launcher-promo').hidden = !show;
+      loadTimeData.overrideValues({'showAppLauncherPromo': show});

[Dan Beam, 2013/03/21 15:45:14]

nit: loadTimeData.overrideValues({showAppLauncherPromo: show});

[MAD, 2013/03/21 16:47:47]

Done.

+    },
+
+    /**
      * Invoked whenever the pages in apps-page-list have changed so that
      * the Slider knows about the new elements.
      */
@@ -490,12 +502,22 @@ cr.define('ntp', function() {
                                       this.appsPages.length - 1)]);
           break;
         case loadTimeData.getInteger('most_visited_page_id'):
-          if (this.mostVisitedPage)
+          if (this.mostVisitedPage) {
             this.cardSlider.selectCardByValue(this.mostVisitedPage);
+          } else if (loadTimeData.getBoolean('showApps')) {
+            // If we don't have a most visited page, we are likely on the
+            // chrome://apps page, so set it appropriately so that we can
+            // display the app launcher promo.
+            this.shownPage = loadTimeData.getInteger('apps_page_id');

[Dan Beam, 2013/03/21 15:45:14]

^ er, shouldn't you be selectCardByValue()'ing here?

[MAD, 2013/03/21 16:47:47]

Yeah, I wasn't sure... Things seems to work anyway, so I tried to make a minimal
change for what wasn't working, i.e., the shownPage state which I need to decide
whether I show the promo box... Now that you asked for it, I changed it, and it
still works... So... fingers crossed... :-)

+          }
           break;
         case loadTimeData.getInteger('suggestions_page_id'):
           if (this.suggestionsPage)
             this.cardSlider.selectCardByValue(this.suggestionsPage);
+          else if (this.mostVisitedPage)
+            this.shownPage = loadTimeData.getInteger('most_visited_page_id');
+          else if (loadTimeData.getBoolean('showApps'))
+            this.shownPage = loadTimeData.getInteger('apps_page_id');
           break;
       }
     },
@@ -651,6 +673,9 @@ cr.define('ntp', function() {
       this.shownPage = shownPage;
       this.shownPageIndex = shownPageIndex;
       chrome.send('pageSelected', [this.shownPage, this.shownPageIndex]);
+      $('app-launcher-promo').hidden =
+        !loadTimeData.getBoolean('showAppLauncherPromo') ||
+        this.shownPage != loadTimeData.getInteger('apps_page_id');

[Dan Beam, 2013/03/21 15:45:14]

please combine this and the same code above into a function and call from both
places

[MAD, 2013/03/21 16:47:47]

Done.
And it made me realize that if we would change the Pref back to true (which
currently can't happen, but might eventually), then we would have been able to
show the promo on non-Apps pages... Good catch! :-)

     },
 
     /**