[WIP] do something :-)

Source/wtf/SizeAssertions.h

+#ifndef WTF_SizeAssertions_h
+#define WTF_SizeAssertions_h
+
+#include "wtf/CPU.h"
+
+namespace WTF {
+
+template<class T, int Expected32BitSize, int Expected64BitSize> struct assert_size {
+    template<int ActualSize, int ExpectedSize> class assert_equal {
+        static_assert(ActualSize == ExpectedSize,
+            "Object size doesn't match expected value, think before making them bigger :-)");
+    };
+#if CPU(32BIT)
+    assert_equal<sizeof(T), Expected32BitSize> tmp;
+#else
+    assert_equal<sizeof(T), Expected64BitSize> tmp;
+#endif
+    enum { Dummy = 1 };
+};
+
+} // namespace WTF
+
+// Some objects have additional members when asserts are enabled, so only check
+// sizes when they are disabled.
+#if ENABLE(ASSERT)
+#define ASSERT_SIZE(className, expected32BitSize, expected64BitSize)
+#else
+#define ASSERT_SIZE(className, expected32BitSize, expected64BitSize) \
+    static_assert(WTF::assert_size<className, expected32BitSize, expected64BitSize>::Dummy, "");
+#endif
+
+#endif /* WTF_SizeAssertions_h */