Enable wallpaper boot animation for boot into sign in too. Add flag to disable it.

chrome/browser/ui/webui/chromeos/login/oobe_ui.cc

Index: chrome/browser/ui/webui/chromeos/login/oobe_ui.cc
diff --git a/chrome/browser/ui/webui/chromeos/login/oobe_ui.cc b/chrome/browser/ui/webui/chromeos/login/oobe_ui.cc
index 9ff15674f5c24ca611fae287e20a2b69085370ac..a35c5767a4ee56d8c15da832456ede0440de2d58 100644
--- a/chrome/browser/ui/webui/chromeos/login/oobe_ui.cc
+++ b/chrome/browser/ui/webui/chromeos/login/oobe_ui.cc
@@ -243,6 +243,15 @@ void OobeUI::GetLocalizedStrings(base::DictionaryValue* localized_strings) {
   else
     localized_strings->SetString("oobeType", "old");
 
+  // If we're not doing boot animation then WebUI should trigger
+  // wallpaper load on boot.
+  if (CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kDisableBootAnimation)) {
+    localized_strings->SetString("bootIntoWallpaper", "on");
+  } else {
+    localized_strings->SetString("bootIntoWallpaper", "off");
+  }
+
   // OobeUI is used for OOBE/login and lock screen.
   if (BaseLoginDisplayHost::default_host())
     localized_strings->SetString("screenType", "login");