[New Multicolumn] Disallow multicol on replaced content and fieldsets.

Source/core/layout/LayoutBlockFlow.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 3082 matching lines @@
     }
 
     if (type == NoFlowThread || multiColumnFlowThread())
         return;
 
     // Ruby elements manage child insertion in a special way, and would mess up insertion of the
     // flow thread. The flow thread needs to be a direct child of the multicol block (|this|).
     if (isRuby())
         return;
 
+    // Fieldsets look for a legend special child (layoutSpecialExcludedChild()). We currently only
+    // support one special child per layout object, and the flow thread would make for a second one.
+    if (isFieldset())
+        return;
+
+    // Form controls are replaced content, and are therefore not supposed to support multicol.
+    if (isFileUploadControl() || isTextControl() || isListBox())
+        return;
+
     LayoutMultiColumnFlowThread* flowThread = createMultiColumnFlowThread(type);
     addChild(flowThread);
 
     // Check that addChild() put the flow thread as a direct child, and didn't do fancy things.
     ASSERT(flowThread->parent() == this);
 
     flowThread->populate();
     LayoutBlockFlowRareData& rareData = ensureRareData();
     ASSERT(!rareData.m_multiColumnFlowThread);
     rareData.m_multiColumnFlowThread = flowThread;
@@ skipping 32 matching lines @@
     FrameView* frameView = document().view();
     LayoutUnit top = (style()->position() == FixedPosition) ? 0 : frameView->scrollOffset().height();
     int visibleHeight = frameView->visibleContentRect(IncludeScrollbars).height();
     if (size().height() < visibleHeight)
         top += (visibleHeight - size().height()) / 2;
     setY(top);
     dialog->setCentered(top);
 }
 
 } // namespace blink