Remove LauncherItemController::Launch, cleanup.

chrome/browser/ui/ash/launcher/chrome_launcher_controller_mus.cc

Index: chrome/browser/ui/ash/launcher/chrome_launcher_controller_mus.cc
diff --git a/chrome/browser/ui/ash/launcher/chrome_launcher_controller_mus.cc b/chrome/browser/ui/ash/launcher/chrome_launcher_controller_mus.cc
index e51e737c3f95dbfa094af909b744ddaf9b15db09..7aea8bb8eebf96b4d100511ab0a75fcabf2aeaa2 100644
--- a/chrome/browser/ui/ash/launcher/chrome_launcher_controller_mus.cc
+++ b/chrome/browser/ui/ash/launcher/chrome_launcher_controller_mus.cc
@@ -34,7 +34,8 @@ class ChromeShelfItemDelegate : public ash::mojom::ShelfItemDelegate {
  private:
   // ash::mojom::ShelfItemDelegate:
   void LaunchItem() override {
-    controller_->LaunchApp(app_id_, ash::LAUNCH_FROM_UNKNOWN, ui::EF_NONE);
+    controller_->LaunchApp(app_id_, std::string(), ash::LAUNCH_FROM_UNKNOWN,
+                           ui::EF_NONE);
   }
   void ExecuteCommand(uint32_t command_id, int32_t event_flags) override {
     NOTIMPLEMENTED();