Add a histogram for tracking web store promo

chrome/browser/dom_ui/app_launcher_handler.h

Index: chrome/browser/dom_ui/app_launcher_handler.h
diff --git a/chrome/browser/dom_ui/app_launcher_handler.h b/chrome/browser/dom_ui/app_launcher_handler.h
index 5a3478ecb88cea16a92e40c4ba8692ed875e9ca5..3e74337adc7a7c8400b59d04ea4a2935aacc987d 100644
--- a/chrome/browser/dom_ui/app_launcher_handler.h
+++ b/chrome/browser/dom_ui/app_launcher_handler.h
@@ -64,6 +64,11 @@ class AppLauncherHandler
   // Callback for the "hideAppPromo" message.
   void HandleHideAppsPromo(const ListValue* args);
 
+  // Callback for the "recordWebStoreLaunch" message.
+  void HandleRecordWebStoreLaunch(const ListValue* args);
+
+  // Callback for the "recordAppLaunch" message.
+  void HandleRecordAppLaunch(const ListValue* args);
  private:
   // ExtensionInstallUI::Delegate implementation, used for receiving
   // notification about uninstall confirmation dialog selections.
@@ -94,6 +99,9 @@ class AppLauncherHandler
   // The id of the extension we are prompting the user about.
   std::string extension_id_prompting_;
 
+  // Whether the promo is currently being shown
+  bool promo_active_;
+
   DISALLOW_COPY_AND_ASSIGN(AppLauncherHandler);
 };