[WIP] do something :-)

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 39 matching lines @@
 #include "core/layout/line/LineWidth.h"
 #include "core/layout/shapes/ShapeOutsideInfo.h"
 #include "core/paint/BlockFlowPainter.h"
 #include "core/paint/ClipScope.h"
 #include "core/paint/DeprecatedPaintLayer.h"
 #include "core/paint/LayoutObjectDrawingRecorder.h"
 #include "core/paint/PaintInfo.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/geometry/TransformState.h"
 #include "platform/text/BidiTextRun.h"
+#include "wtf/SizeAssertions.h"
 
 namespace blink {
 
+ASSERT_SIZE(LayoutBlockFlow::MarginValues, 16, 16);
+
 bool LayoutBlockFlow::s_canPropagateFloatIntoSibling = false;
 
-struct SameSizeAsMarginInfo {
-    uint16_t bitfields;
-    LayoutUnit margins[2];
-};
-
-static_assert(sizeof(LayoutBlockFlow::MarginValues) == sizeof(LayoutUnit[4]), "MarginValues should stay small");
-
 class MarginInfo {
     // Collapsing flags for whether we can collapse our margins with our children's margins.
     bool m_canCollapseWithChildren : 1;
     bool m_canCollapseMarginBeforeWithChildren : 1;
     bool m_canCollapseMarginAfterWithChildren : 1;
     bool m_canCollapseMarginAfterWithLastChild: 1;
 
     // Whether or not we are a quirky container, i.e., do we collapse away top and bottom
     // margins in our container. Table cells and the body are the common examples. We
     // also have a custom style property for Safari RSS to deal with TypePad blog articles.
@@ skipping 64 matching lines @@
     bool determinedMarginBeforeQuirk() const { return m_determinedMarginBeforeQuirk; }
     bool hasMarginBeforeQuirk() const { return m_hasMarginBeforeQuirk; }
     bool hasMarginAfterQuirk() const { return m_hasMarginAfterQuirk; }
     LayoutUnit positiveMargin() const { return m_positiveMargin; }
     LayoutUnit negativeMargin() const { return m_negativeMargin; }
     bool discardMargin() const { return m_discardMargin; }
     LayoutUnit margin() const { return m_positiveMargin - m_negativeMargin; }
     void setLastChildIsSelfCollapsingBlockWithClearance(bool value) { m_lastChildIsSelfCollapsingBlockWithClearance = value; }
     bool lastChildIsSelfCollapsingBlockWithClearance() const { return m_lastChildIsSelfCollapsingBlockWithClearance; }
 };
+
+ASSERT_SIZE(MarginInfo, 12, 12);
+
 static bool inNormalFlow(LayoutBox* child)
 {
     LayoutBlock* curr = child->containingBlock();
     LayoutView* layoutView = child->view();
     while (curr && curr != layoutView) {
         if (curr->isLayoutFlowThread())
             return true;
         if (curr->isFloatingOrOutOfFlowPositioned())
             return false;
         curr = curr->containingBlock();
     }
     return true;
 }
 
 LayoutBlockFlow::LayoutBlockFlow(ContainerNode* node)
     : LayoutBlock(node)
 {
-    static_assert(sizeof(MarginInfo) == sizeof(SameSizeAsMarginInfo), "MarginInfo should stay small");
     setChildrenInline(true);
 }
 
 LayoutBlockFlow::~LayoutBlockFlow()
 {
 }
 
 LayoutBlockFlow* LayoutBlockFlow::createAnonymous(Document* document)
 {
     LayoutBlockFlow* layoutBlockFlow = new LayoutBlockFlow(nullptr);
@@ skipping 2886 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