Convert HTMLFrameOwnerElement and FocusController to use Frame.

Source/core/page/PageSerializer.cpp

Index: Source/core/page/PageSerializer.cpp
diff --git a/Source/core/page/PageSerializer.cpp b/Source/core/page/PageSerializer.cpp
index 6cff82f3532b51622b593c30c1776647c8eedd4c..befcb03877f19603d86cdeefae583d53d6178a1f 100644
--- a/Source/core/page/PageSerializer.cpp
+++ b/Source/core/page/PageSerializer.cpp
@@ -154,7 +154,7 @@ void SerializerMarkupAccumulator::appendCustomAttributes(StringBuilder& out, con
         return;
 
     const HTMLFrameOwnerElement& frameOwner = toHTMLFrameOwnerElement(element);
-    LocalFrame* frame = frameOwner.contentFrame();
+    LocalFrame* frame = toLocalFrame(frameOwner.contentFrame());
     if (!frame)
         return;