5 files changed, 94 insertions, 0 deletions

diff --git a/chrome/browser/dom_ui/app_launcher_handler.cc b/chrome/browser/dom_ui/app_launcher_handler.cc
index e834754..674d951 100644
--- a/chrome/browser/dom_ui/app_launcher_handler.cc
+++ b/chrome/browser/dom_ui/app_launcher_handler.cc
@@ -121,6 +121,14 @@ void AppLauncherHandler::CreateAppInfo(Extension* extension,
   value->SetInteger("launch_container", extension->launch_container());
   value->SetInteger("launch_type",
       extension_prefs->GetLaunchType(extension->id()));
+
+  int app_launch_index = extension_prefs->GetAppLaunchIndex(extension->id());
+  if (app_launch_index == -1) {
+    // Make sure every app has a launch index (some predate the launch index).
+    app_launch_index = extension_prefs->GetNextAppLaunchIndex();
+    extension_prefs->SetAppLaunchIndex(extension->id(), app_launch_index);
+  }
+  value->SetInteger("app_launch_index", app_launch_index);
 }
 
 void AppLauncherHandler::FillAppDictionary(DictionaryValue* dictionary) {
diff --git a/chrome/browser/extensions/extension_prefs.cc b/chrome/browser/extensions/extension_prefs.cc
index 9c7a1cf..2381c01 100644
--- a/chrome/browser/extensions/extension_prefs.cc
+++ b/chrome/browser/extensions/extension_prefs.cc
@@ -79,6 +79,9 @@ const char kWebStoreLogin[] = "extensions.webstore_login";
 // used for apps.
 const char kPrefLaunchType[] = "launchType";
 
+// A preference determining the order of which the apps appear on the NTP.
+const char kPrefAppLaunchIndex[] = "app_launcher_index";
+
 }  // namespace
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -538,6 +541,8 @@ void ExtensionPrefs::OnExtensionInstalled(
     UpdateExtensionPref(id, kPrefManifest,
                         extension->manifest_value()->DeepCopy());
   }
+  UpdateExtensionPref(id, kPrefAppLaunchIndex,
+                      Value::CreateIntegerValue(GetNextAppLaunchIndex()));
   SavePrefsAndNotify();
 }
 
@@ -864,6 +869,37 @@ void ExtensionPrefs::SetWebStoreLogin(const std::string& login) {
   SavePrefsAndNotify();
 }
 
+int ExtensionPrefs::GetAppLaunchIndex(const std::string& extension_id) {
+  int value;
+  if (ReadExtensionPrefInteger(extension_id, kPrefAppLaunchIndex, &value))
+    return value;
+
+  return -1;
+}
+
+void ExtensionPrefs::SetAppLaunchIndex(const std::string& extension_id,
+                                       int index) {
+  DCHECK_GE(index, 0);
+  UpdateExtensionPref(extension_id, kPrefAppLaunchIndex,
+                      Value::CreateIntegerValue(index));
+  SavePrefsAndNotify();
+}
+
+int ExtensionPrefs::GetNextAppLaunchIndex() {
+  const DictionaryValue* extensions = prefs_->GetDictionary(kExtensionsPref);
+  if (!extensions)
+    return 0;
+
+  int max_value = -1;
+  for (DictionaryValue::key_iterator extension_id = extensions->begin_keys();
+       extension_id != extensions->end_keys(); ++extension_id) {
+    int value = GetAppLaunchIndex(*extension_id);
+    if (value > max_value)
+      max_value = value;
+  }
+  return max_value + 1;
+}
+
 // static
 void ExtensionPrefs::RegisterUserPrefs(PrefService* prefs) {
   prefs->RegisterDictionaryPref(kExtensionsPref);
diff --git a/chrome/browser/extensions/extension_prefs.h b/chrome/browser/extensions/extension_prefs.h
index 7bfe9eb..97547ea 100644
--- a/chrome/browser/extensions/extension_prefs.h
+++ b/chrome/browser/extensions/extension_prefs.h
@@ -174,6 +174,19 @@ class ExtensionPrefs {
   bool GetWebStoreLogin(std::string* result);
   void SetWebStoreLogin(const std::string& login);
 
+  // Get the application launch index for an extension with |extension_id|. This
+  // determines the order of which the applications appear on the New Tab Page.
+  // A value of 0 generally indicates top left. If the extension has no launch
+  // index a -1 value is returned.
+  int GetAppLaunchIndex(const std::string& extension_id);
+
+  // Sets a specific launch index for an extension with |extension_id|.
+  void SetAppLaunchIndex(const std::string& extension_id, int index);
+
+  // Gets the next available application launch index. This is 1 higher than the
+  // highest current application launch index found.
+  int GetNextAppLaunchIndex();
+
   static void RegisterUserPrefs(PrefService* prefs);
 
   // The underlying PrefService.
diff --git a/chrome/browser/extensions/extension_prefs_unittest.cc b/chrome/browser/extensions/extension_prefs_unittest.cc
index 11194e7..c9f9336 100644
--- a/chrome/browser/extensions/extension_prefs_unittest.cc
+++ b/chrome/browser/extensions/extension_prefs_unittest.cc
@@ -334,3 +334,36 @@ class ExtensionPrefsOnExtensionInstalled : public ExtensionPrefsTest {
 };
 TEST_F(ExtensionPrefsOnExtensionInstalled,
        ExtensionPrefsOnExtensionInstalled) {}
+
+class ExtensionPrefsAppLaunchIndex : public ExtensionPrefsTest {
+public:
+  virtual void Initialize() {
+    // No extensions yet.
+    EXPECT_EQ(0, prefs()->GetNextAppLaunchIndex());
+
+    extension_.reset(prefs_.AddExtension("on_extension_installed"));
+    EXPECT_EQ(Extension::ENABLED,
+        prefs()->GetExtensionState(extension_->id()));
+    prefs()->OnExtensionInstalled(extension_.get(),
+        Extension::ENABLED, false);
+  }
+
+  virtual void Verify() {
+    int launch_index = prefs()->GetAppLaunchIndex(extension_->id());
+    // Extension should have been assigned a launch index > 0.
+    EXPECT_GT(launch_index, 0);
+    EXPECT_EQ(launch_index + 1, prefs()->GetNextAppLaunchIndex());
+    // Set a new launch index of one higher and verify.
+    prefs()->SetAppLaunchIndex(extension_->id(),
+        prefs()->GetNextAppLaunchIndex());
+    int new_launch_index = prefs()->GetAppLaunchIndex(extension_->id());
+    EXPECT_EQ(launch_index + 1, new_launch_index);
+
+    // This extension doesn't exist, so it should return -1.
+    EXPECT_EQ(-1, prefs()->GetAppLaunchIndex("foo"));
+  }
+
+private:
+  scoped_ptr<Extension> extension_;
+};
+TEST_F(ExtensionPrefsAppLaunchIndex, ExtensionPrefsAppLaunchIndex) {}
diff --git a/chrome/browser/resources/ntp/apps.js b/chrome/browser/resources/ntp/apps.js
index e6f79a2..da91af7 100644
--- a/chrome/browser/resources/ntp/apps.js
+++ b/chrome/browser/resources/ntp/apps.js
@@ -14,6 +14,10 @@ function getAppsCallback(data) {
     appsSectionContent.removeChild(appsSectionContent.lastChild);
   }
 
+  data.apps.sort(function(a,b) {
+    return a.app_launch_index - b.app_launch_index
+  });
+
   clearClosedMenu(apps.menu);
   if (data.apps.length == 0) {
     appsSection.classList.add('disabled');