Have Element::ensureUserAgentShadowRoot() return a reference

Source/core/html/HTMLInputElement.cpp

Index: Source/core/html/HTMLInputElement.cpp
diff --git a/Source/core/html/HTMLInputElement.cpp b/Source/core/html/HTMLInputElement.cpp
index a4ceaef115b2a43fe493ac5e63ac26dbe381290f..2d087dc8ca572ac4b17bb3abbeeecb7963c9407a 100644
--- a/Source/core/html/HTMLInputElement.cpp
+++ b/Source/core/html/HTMLInputElement.cpp
@@ -141,7 +141,7 @@ HTMLImageLoader* HTMLInputElement::imageLoader()
     return m_imageLoader.get();
 }
 
-void HTMLInputElement::didAddUserAgentShadowRoot(ShadowRoot*)
+void HTMLInputElement::didAddUserAgentShadowRoot(ShadowRoot&)
 {
     m_inputType->createShadowSubtree();
 }