Have Node::document() return a reference instead of a pointer

Source/core/html/ImageInputType.cpp

Index: Source/core/html/ImageInputType.cpp
diff --git a/Source/core/html/ImageInputType.cpp b/Source/core/html/ImageInputType.cpp
index 6711feea89148d1893007b60dfe54e70bb7785cb..06ada941de3b14c6facd5527998969ebfd0152c2 100644
--- a/Source/core/html/ImageInputType.cpp
+++ b/Source/core/html/ImageInputType.cpp
@@ -189,7 +189,7 @@ unsigned ImageInputType::height() const
         }
     }
 
-    element->document()->updateLayout();
+    element->document().updateLayout();
 
     RenderBox* box = element->renderBox();
     return box ? adjustForAbsoluteZoom(box->contentHeight(), box) : 0;
@@ -213,7 +213,7 @@ unsigned ImageInputType::width() const
         }
     }
 
-    element->document()->updateLayout();
+    element->document().updateLayout();
 
     RenderBox* box = element->renderBox();
     return box ? adjustForAbsoluteZoom(box->contentWidth(), box) : 0;