Revert of Support margin-top for legend in fieldset.

third_party/WebKit/Source/core/layout/LayoutFieldset.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006 Apple Computer, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 156 matching lines @@
     }
 
     setLogicalLeftForChild(*legend, logicalLeft);
 
     LayoutUnit fieldsetBorderBefore = LayoutUnit(borderBefore());
     LayoutUnit legendLogicalHeight = logicalHeightForChild(*legend);
 
     LayoutUnit legendLogicalTop;
     LayoutUnit collapsedLegendExtent;
     LayoutUnit innerBlockPadding;
-
-    if (legendLogicalHeight < fieldsetBorderBefore) {
-      // Center legend in fieldset border
+    // FIXME: We need to account for the legend's margin before too.
+    if (fieldsetBorderBefore > legendLogicalHeight) {
+      // The <legend> is smaller than the associated fieldset before border
+      // so the latter determines positioning of the <legend>. The sizing
+      // depends on the legend's margins as we want to still follow the
+      // author's cues.
+      // Firefox completely ignores the margins in this case which seems wrong.
       legendLogicalTop = (fieldsetBorderBefore - legendLogicalHeight) / 2;
+      collapsedLegendExtent = max<LayoutUnit>(
+          fieldsetBorderBefore, legendLogicalTop + legendLogicalHeight +
+                                    marginAfterForChild(*legend));
+      innerBlockPadding = marginAfterForChild(*legend)
+                              ? marginAfterForChild(*legend) - legendLogicalTop
+                              : LayoutUnit();
+    } else {
+      collapsedLegendExtent =
+          legendLogicalHeight + marginAfterForChild(*legend);
+      innerBlockPadding =
+          legendLogicalHeight - borderAfter() + marginAfterForChild(*legend);
     }
 
-    // Calculate how much legend + bottom margin sticks below the fieldset
-    // border
-    innerBlockPadding = (legendLogicalTop + legendLogicalHeight +
-                         marginAfterForChild(*legend) - fieldsetBorderBefore)
-                            .clampNegativeToZero();
-
-    if (legendLogicalTop < marginBeforeForChild(*legend)) {
-      // legend margin pushes everything down
-      innerBlockPadding += marginBeforeForChild(*legend) - legendLogicalTop;
-      legendLogicalTop = marginBeforeForChild(*legend);
-    }
-
-    collapsedLegendExtent =
-        std::max(fieldsetBorderBefore, marginBeforeForChild(*legend) +
-                                           legendLogicalHeight +
-                                           marginAfterForChild(*legend));
-
     if (m_innerBlock)
       setInnerBlockPadding(isHorizontalWritingMode(), m_innerBlock,
                            innerBlockPadding);
     setLogicalTopForChild(*legend, legendLogicalTop);
     setLogicalHeight(paddingBefore() + collapsedLegendExtent);
 
     if (legend->frameRect() != oldLegendFrameRect) {
       // We need to invalidate the fieldset border if the legend's frame
       // changed.
       setShouldDoFullPaintInvalidation();
@@ skipping 86 matching lines @@
     LayoutFlexibleBox::removeChild(oldChild);
     m_innerBlock = nullptr;
   } else if (oldChild->parent() == this) {
     LayoutFlexibleBox::removeChild(oldChild);
   } else if (m_innerBlock) {
     m_innerBlock->removeChild(oldChild);
   }
 }
 
 }  // namespace blink