Fix bad use of OffsetFrom that fails on ARM (sizeof(Object) wasn't 1).

Review URL: http://codereview.chromium.org/1043001

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4141 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/heap-inl.h

@@ -133,7 +133,8 @@ Object* Heap::AllocateRawMap() {
 #ifdef DEBUG
   if (!result->IsFailure()) {
     // Maps have their own alignment.
-    CHECK((OffsetFrom(result) & kMapAlignmentMask) == kHeapObjectTag);
+    CHECK_EQ(static_cast<intptr_t>(kHeapObjectTag),
+             reinterpret_cast<intptr_t>(result) & kMapAlignmentMask);
   }
 #endif
   return result;