Backed out changeset 3411f1c818f6 (bug 1374629) for build bustage a=b…

…ackout

MozReview-Commit-ID: GHWdfD0h8LI

mfbt/NotNull.h

@@ -63,7 +63,6 @@
 // for the last one, where the handle type is |void|. See below.
 
 #include "mozilla/Assertions.h"
-#include <stddef.h>
 
 namespace mozilla {
 
@@ -115,12 +114,7 @@ class NotNull
 
   // Construct/assign from another NotNull with a compatible base pointer type.
   template <typename U>
-  MOZ_IMPLICIT NotNull(const NotNull<U>& aOther) : mBasePtr(aOther.get()) {
-    static_assert(sizeof(T) == sizeof(NotNull<T>),
-                  "NotNull must have zero space overhead.");
-    static_assert(offsetof(NotNull<T>, mBasePtr) == 0,
-                  "mBasePtr must have zero offset.");
-  }
+  MOZ_IMPLICIT NotNull(const NotNull<U>& aOther) : mBasePtr(aOther.get()) {}
 
   // Default copy/move construction and assignment.
   NotNull(const NotNull<T>&) = default;