Pass implementation object to supplemental classes by reference

Source/web/WebFrameImpl.cpp

Index: Source/web/WebFrameImpl.cpp
diff --git a/Source/web/WebFrameImpl.cpp b/Source/web/WebFrameImpl.cpp
index 93f9780c97add99b26a98f3b4f0d61a8cafd9e1b..993f43d2b54a20fdbde21c5e1f79ac17d5ed5793 100644
--- a/Source/web/WebFrameImpl.cpp
+++ b/Source/web/WebFrameImpl.cpp
@@ -754,8 +754,9 @@ WebFrame* WebFrameImpl::findChildByExpression(const WebString& xpath) const
         return 0;
 
     Document* document = frame()->document();
+    ASSERT(document);
 
-    RefPtrWillBeRawPtr<XPathResult> xpathResult = DocumentXPathEvaluator::evaluate(document, xpath, document, 0, XPathResult::ORDERED_NODE_ITERATOR_TYPE, 0, IGNORE_EXCEPTION);
+    RefPtrWillBeRawPtr<XPathResult> xpathResult = DocumentXPathEvaluator::evaluate(*document, xpath, document, 0, XPathResult::ORDERED_NODE_ITERATOR_TYPE, 0, IGNORE_EXCEPTION);
     if (!xpathResult)
         return 0;