Have DOMImplementation::document() return reference.

Source/bindings/scripts/code_generator_v8.pm

Index: Source/bindings/scripts/code_generator_v8.pm
diff --git a/Source/bindings/scripts/code_generator_v8.pm b/Source/bindings/scripts/code_generator_v8.pm
index df03adfd0a6d87a8907bc92e76b2d07897c52fcf..87098f76170f92ad863bc4c072d3b09f7840c158 100644
--- a/Source/bindings/scripts/code_generator_v8.pm
+++ b/Source/bindings/scripts/code_generator_v8.pm
@@ -505,7 +505,7 @@ sub HeaderFilesForInterface
 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
@@ -576,11 +576,26 @@ END
 END
     }
 
-    $code .= <<END;
+    my $isReachableReferenceMethod = $interface->extendedAttributes->{"SetWrapperReferenceFromReference"};

[Inactive, 2014/02/04 14:31:40]

I would try to merge this as much as possible with the SetWrapperReferenceFrom
code to avoid duplication.

+    if ($isReachableReferenceMethod) {
+        AddToImplIncludes("bindings/v8/V8GCController.h");
+        AddToImplIncludes("core/dom/Element.h");
+        $code .= <<END;
+    Node* root = V8GCController::opaqueRootForGC(&impl->${isReachableReferenceMethod}(), isolate);
+    isolate->SetReferenceFromGroup(v8::UniqueId(reinterpret_cast<intptr_t>(root)), wrapper);
+}
+
+END
+    }
+
+    if (!$isReachableReferenceMethod) {
+        $code .= <<END;
     setObjectGroup(object, wrapper, isolate);
 }
 
 END
+    }
+
     $implementation{nameSpaceWebCore}->add($code);
 }