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

Source/core/paint/ViewDisplayList.cpp

Index: Source/core/paint/ViewDisplayList.cpp
diff --git a/Source/core/paint/ViewDisplayList.cpp b/Source/core/paint/ViewDisplayList.cpp
index 4e64ec228643a6335bab7769fc9e846113cb0b48..0cf0f353726776d8d0e48b44063ce1e761a1e5cd 100644
--- a/Source/core/paint/ViewDisplayList.cpp
+++ b/Source/core/paint/ViewDisplayList.cpp
@@ -5,6 +5,9 @@
 #include "config.h"
 #include "core/paint/ViewDisplayList.h"
 
+#include "core/frame/LocalFrame.h"
+#include "core/rendering/RenderLayer.h"
+#include "core/rendering/RenderView.h"
 #include "platform/NotImplemented.h"
 #include "platform/RuntimeEnabledFeatures.h"
 
@@ -55,6 +58,31 @@ void ViewDisplayList::updatePaintList()
     notImplemented();
 }
 
+ViewDisplayList& ViewDisplayList::fromRenderObject(const RenderObject* renderer)
+{
+    ASSERT(renderer);
+
+    RenderView* renderView = renderer->view();
+    ASSERT(renderView);
+
+    FrameView* frameView = renderView->frameView();
+    ASSERT(frameView);
+
+    LocalFrame* localRoot = frameView->frame().localRoot();
+    ASSERT(localRoot);
+
+    FrameView* localRootView = localRoot->view();
+    ASSERT(localRootView);
+
+    return localRootView->viewDisplayList();
+}
+
+ViewDisplayList& ViewDisplayList::fromRenderLayer(const RenderLayer* layer)
+{
+    ASSERT(layer);
+    return fromRenderObject(layer->renderer());
+}
+
 #ifndef NDEBUG
 WTF::String DisplayItem::typeAsDebugString(DisplayItem::Type type)
 {