RenderBlock::isSelfCollapsingBlock() should only be used when an object does not require layout.

Source/core/rendering/RenderTextControlPlaceholder.h

Index: Source/core/rendering/RenderTextControlPlaceholder.h
diff --git a/Source/core/svg/SVGDescElement.h b/Source/core/rendering/RenderTextControlPlaceholder.h
similarity index 60%
copy from Source/core/svg/SVGDescElement.h
copy to Source/core/rendering/RenderTextControlPlaceholder.h
index 6a68eb7d798f92cbbada21148741825cde1d83f5..a56b82b715ca52fa09c7f5483fb9ad4a14615ced 100644
--- a/Source/core/svg/SVGDescElement.h
+++ b/Source/core/rendering/RenderTextControlPlaceholder.h
@@ -1,6 +1,5 @@
 /*
- * Copyright (C) 2004, 2005 Nikolas Zimmermann <zimmermann@kde.org>
- * Copyright (C) 2004, 2005 Rob Buis <buis@kde.org>
+ * Copyright (C) 2014 Robert Hogan <robert@roberthogan.net>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ -18,25 +17,23 @@
  * Boston, MA 02110-1301, USA.
  */
 
-#ifndef SVGDescElement_h
-#define SVGDescElement_h
+#ifndef RenderTextControlPlaceholder_h
+#define RenderTextControlPlaceholder_h
 
-#include "core/svg/SVGElement.h"
+#include "core/rendering/RenderBlockFlow.h"
 
 namespace WebCore {
 
-class SVGDescElement FINAL : public SVGElement {
-public:
-    static PassRefPtr<SVGDescElement> create(Document&);
-
-    String description() const;
-
-private:
-    explicit SVGDescElement(Document&);
 
-    virtual bool rendererIsNeeded(const RenderStyle&) OVERRIDE { return false; }
+class RenderTextControlPlaceholder FINAL : public RenderBlockFlow {
+public:
+    explicit RenderTextControlPlaceholder(Element*);
+    virtual ~RenderTextControlPlaceholder();
+    virtual bool isSelfCollapsingBlock() const OVERRIDE FINAL { return false; }

[ojan, 2014/01/14 00:34:18]

I think this deserve a comment explaining why we override it.

Also, can you point me at the code that you reference in the change description
that does the parent's layout before the child?

[rhogan, 2014/01/14 19:23:01]

Yes: the placeholder is not laid out until the end of 
RenderTextControlSingleLine::layout().

 };
 
+DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderTextControlPlaceholder, isTableCaption());

[ojan, 2014/01/14 00:34:18]

isTableCaption?

+
 } // namespace WebCore
 
-#endif
+#endif // RenderTextControlPlaceholder_h