[WIP] do something :-)

Source/core/layout/LayoutBlockFlow.cpp

Index: Source/core/layout/LayoutBlockFlow.cpp
diff --git a/Source/core/layout/LayoutBlockFlow.cpp b/Source/core/layout/LayoutBlockFlow.cpp
index fe9339df5d8e2767186d1a764933139a4662d2e6..b1c0764f63008768ec0f17f46c531bf117b8001e 100644
--- a/Source/core/layout/LayoutBlockFlow.cpp
+++ b/Source/core/layout/LayoutBlockFlow.cpp
@@ -57,17 +57,13 @@
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/geometry/TransformState.h"
 #include "platform/text/BidiTextRun.h"
+#include "wtf/SizeAssertions.h"
 
 namespace blink {
 
-bool LayoutBlockFlow::s_canPropagateFloatIntoSibling = false;
-
-struct SameSizeAsMarginInfo {
-    uint16_t bitfields;
-    LayoutUnit margins[2];
-};
+ASSERT_SIZE(LayoutBlockFlow::MarginValues, 16, 16);
 
-static_assert(sizeof(LayoutBlockFlow::MarginValues) == sizeof(LayoutUnit[4]), "MarginValues should stay small");
+bool LayoutBlockFlow::s_canPropagateFloatIntoSibling = false;
 
 class MarginInfo {
     // Collapsing flags for whether we can collapse our margins with our children's margins.
@@ -153,6 +149,9 @@ public:
     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();
@@ -170,7 +169,6 @@ static bool inNormalFlow(LayoutBox* child)
 LayoutBlockFlow::LayoutBlockFlow(ContainerNode* node)
     : LayoutBlock(node)
 {
-    static_assert(sizeof(MarginInfo) == sizeof(SameSizeAsMarginInfo), "MarginInfo should stay small");
     setChildrenInline(true);
 }