Add const versions of some toHTMLFooElement().

Source/core/dom/Node.cpp

Index: Source/core/dom/Node.cpp
diff --git a/Source/core/dom/Node.cpp b/Source/core/dom/Node.cpp
index 2bc7123aa6726290d5c648d1121d86e115467482..7a883fbbb0dc81a1e703bce489c5f29ead8bdea9 100644
--- a/Source/core/dom/Node.cpp
+++ b/Source/core/dom/Node.cpp
@@ -2006,15 +2006,15 @@ static void showSubTreeAcrossFrame(const Node* node, const Node* markedNode, con
         fputs("*", stderr);
     fputs(indent.utf8().data(), stderr);
     node->showNode();
-     if (node->isShadowRoot()) {
-         if (ShadowRoot* youngerShadowRoot = toShadowRoot(node)->youngerShadowRoot())
-             showSubTreeAcrossFrame(youngerShadowRoot, markedNode, indent + "\t");
-     } else {
-         if (node->isFrameOwnerElement())
-             showSubTreeAcrossFrame(static_cast<const HTMLFrameOwnerElement*>(node)->contentDocument(), markedNode, indent + "\t");
-         if (ShadowRoot* oldestShadowRoot = oldestShadowRootFor(node))
-             showSubTreeAcrossFrame(oldestShadowRoot, markedNode, indent + "\t");
-     }
+    if (node->isShadowRoot()) {
+        if (ShadowRoot* youngerShadowRoot = toShadowRoot(node)->youngerShadowRoot())
+            showSubTreeAcrossFrame(youngerShadowRoot, markedNode, indent + "\t");
+    } else {
+        if (node->isFrameOwnerElement())
+            showSubTreeAcrossFrame(toHTMLFrameOwnerElement(node)->contentDocument(), markedNode, indent + "\t");
+        if (ShadowRoot* oldestShadowRoot = oldestShadowRootFor(node))
+            showSubTreeAcrossFrame(oldestShadowRoot, markedNode, indent + "\t");
+    }
     for (Node* child = node->firstChild(); child; child = child->nextSibling())
         showSubTreeAcrossFrame(child, markedNode, indent + "\t");
 }