Re-enable main-frame and subframe CSSOM smooth scroll layout tests

Source/core/frame/FrameView.cpp

Index: Source/core/frame/FrameView.cpp
diff --git a/Source/core/frame/FrameView.cpp b/Source/core/frame/FrameView.cpp
index a37325b161e2459a70afe0803b4ad6ee2374dfa8..c0c6760e140459214c2c7f0483a679529c9d9294 100644
--- a/Source/core/frame/FrameView.cpp
+++ b/Source/core/frame/FrameView.cpp
@@ -1553,7 +1553,7 @@ void FrameView::setScrollPosition(const DoublePoint& scrollPoint, ScrollBehavior
         return;
 
     if (scrollBehavior == ScrollBehaviorAuto) {
-        RenderObject* renderer = m_frame->document()->documentElement() ? m_frame->document()->documentElement()->renderer() : 0;
+        RenderObject* renderer = m_frame->document()->body() ? m_frame->document()->body()->renderer() : 0;

[jochen (gone - plz use gerrit), 2015/02/04 12:49:17]

should this maybe depend on the ScrollTopLeftInteropt runtime feature?

[ajuma, 2015/02/04 15:08:10]

Good point, done.

         if (renderer && renderer->style()->scrollBehavior() == ScrollBehaviorSmooth)
             scrollBehavior = ScrollBehaviorSmooth;
         else