[WIP] Adding support for <iframe>s to slimming paint.

Source/core/frame/Frame.cpp

Index: Source/core/frame/Frame.cpp
diff --git a/Source/core/frame/Frame.cpp b/Source/core/frame/Frame.cpp
index cc04f692752cab7a1c1c01af6fb82ed9b16099d9..e0ae2e401941a29683456d9188d4dd1e6cd61902 100644
--- a/Source/core/frame/Frame.cpp
+++ b/Source/core/frame/Frame.cpp
@@ -132,6 +132,14 @@ bool Frame::isLocalRoot() const
     return tree().parent()->isRemoteFrame();
 }
 
+LocalFrame* Frame::localRoot() const
+{
+    Frame* frame = const_cast<Frame*>(this);
+    while (frame && !frame->isLocalRoot())
+        frame = frame->tree().parent();
+    return toLocalFrame(frame);
+}
+
 HTMLFrameOwnerElement* Frame::deprecatedLocalOwner() const
 {
     return m_owner && m_owner->isLocal() ? toHTMLFrameOwnerElement(m_owner) : 0;