Have DOMImplementation::document() return reference.

Source/bindings/scripts/code_generator_v8.pm

 # Copyright (C) 2005, 2006 Nikolas Zimmermann <zimmermann@kde.org>
 # Copyright (C) 2006 Anders Carlsson <andersca@mac.com>
 # Copyright (C) 2006 Samuel Weinig <sam.weinig@gmail.com>
 # Copyright (C) 2006 Alexey Proskuryakov <ap@webkit.org>
 # Copyright (C) 2006 Apple Computer, Inc.
 # Copyright (C) 2007, 2008, 2009, 2012 Google Inc.
 # Copyright (C) 2009 Cameron McCormack <cam@mcc.id.au>
 # Copyright (C) Research In Motion Limited 2010. All rights reserved.
 # Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
 # Copyright (C) 2012 Ericsson AB. All rights reserved.
@@ skipping 497 matching lines @@
         my $idlFilename = Cwd::abs_path(IDLFileForInterface($interfaceName)) or die("Could NOT find IDL file for interface \"$interfaceName\" $!\n");
         my $idlRelPath = File::Spec->abs2rel($idlFilename, $sourceRoot);
         push(@includes, dirname($idlRelPath) . "/" . $implClassName . ".h");
     }
     return @includes;
 }
 
 sub NeedsVisitDOMWrapper
 {
     my $interface = shift;
-    return ExtendedAttributeContains($interface->extendedAttributes->{"Custom"}, "VisitDOMWrapper") || $interface->extendedAttributes->{"SetWrapperReferenceFrom"} || $interface->extendedAttributes->{"SetWrapperReferenceTo"} || SVGTypeNeedsToHoldContextElement($interface->name);
+    return ExtendedAttributeContains($interface->extendedAttributes->{"Custom"}, "VisitDOMWrapper") || $interface->extendedAttributes->{"SetWrapperReferenceFrom"} || $interface->extendedAttributes->{"SetWrapperReferenceFromReference"} || $interface->extendedAttributes->{"SetWrapperReferenceTo"} || SVGTypeNeedsToHoldContextElement($interface->name);
 }
 
 sub GenerateVisitDOMWrapper
 {
     my $interface = shift;
     my $implClassName = GetImplName($interface);
     my $v8ClassName = GetV8ClassName($interface);
 
     if (ExtendedAttributeContains($interface->extendedAttributes->{"Custom"}, "VisitDOMWrapper")) {
         return;
@@ skipping 38 matching lines @@
     ${setReferenceType}* ${setReferenceName} = impl->${setReferenceName}();
     if (${setReferenceName}) {
         if (!DOMDataStore::containsWrapper<${setReferenceV8Type}>(${setReferenceName}, isolate))
             wrap(${setReferenceName}, creationContext, isolate);
         DOMDataStore::setWrapperReference<${setReferenceV8Type}>(wrapper, ${setReferenceName}, isolate);
     }
 END
     }
 
     my $isReachableMethod = $interface->extendedAttributes->{"SetWrapperReferenceFrom"};
-    if ($isReachableMethod) {
+    my $isReachableReferenceMethod = $interface->extendedAttributes->{"SetWrapperReferenceFromReference"};
+
+    if ($isReachableMethod || $isReachableReferenceMethod) {
         AddToImplIncludes("bindings/v8/V8GCController.h");
         AddToImplIncludes("core/dom/Element.h");
-        $code .= <<END;
+        if ($isReachableMethod) {
+            $code .= <<END;
     if (Node* owner = impl->${isReachableMethod}()) {
         Node* root = V8GCController::opaqueRootForGC(owner, isolate);
         isolate->SetReferenceFromGroup(v8::UniqueId(reinterpret_cast<intptr_t>(root)), wrapper);
         return;
     }
 END
+        } else {
+            $code .= <<END;
+    Node* root = V8GCController::opaqueRootForGC(&impl->${isReachableReferenceMethod}(), isolate);
+    isolate->SetReferenceFromGroup(v8::UniqueId(reinterpret_cast<intptr_t>(root)), wrapper);
+}
+
+END
+        }
     }
 
-    $code .= <<END;
+    if (!$isReachableReferenceMethod) {
+        $code .= <<END;
     setObjectGroup(object, wrapper, isolate);
 }
 
 END
+    }
+
     $implementation{nameSpaceWebCore}->add($code);
 }
 
 sub GetSVGPropertyTypes
 {
     my $implType = shift;
 
     my $svgPropertyType;
     my $svgListPropertyType;
     my $svgNativeType;
@@ skipping 5882 matching lines @@
         if ($parameter->type eq "SerializedScriptValue") {
             return 1;
         } elsif (IsIntegerType($parameter->type)) {
             return 1;
         }
     }
     return 0;
 }
 
 1;