WIP: Eliminate event.target() usage from TrayEventFilter

chrome/browser/ui/ash/chrome_shell_delegate.cc

Index: chrome/browser/ui/ash/chrome_shell_delegate.cc
diff --git a/chrome/browser/ui/ash/chrome_shell_delegate.cc b/chrome/browser/ui/ash/chrome_shell_delegate.cc
index c58d4e6067de838aabe0588cd841d6ea5f3d07f4..1bf20008d13fab693d8d14ee18eaf275df3f3d89 100644
--- a/chrome/browser/ui/ash/chrome_shell_delegate.cc
+++ b/chrome/browser/ui/ash/chrome_shell_delegate.cc
@@ -6,6 +6,7 @@
 
 #include <stddef.h>
 
+#include "ash/container_delegate_aura.h"
 #include "ash/content/gpu_support_impl.h"
 #include "ash/pointer_watcher_delegate_aura.h"
 #include "ash/session/session_state_delegate.h"
@@ -156,6 +157,11 @@ ash::ShelfDelegate* ChromeShellDelegate::CreateShelfDelegate(
   return shelf_delegate_;
 }
 
+std::unique_ptr<ash::ContainerDelegate>
+ChromeShellDelegate::CreateContainerDelegate() {
+  return base::WrapUnique(new ash::ContainerDelegateAura);
+}
+
 std::unique_ptr<ash::PointerWatcherDelegate>
 ChromeShellDelegate::CreatePointerWatcherDelegate() {
   return base::WrapUnique(new ash::PointerWatcherDelegateAura);