Add more instrumentation for Code::CopyFrom crasher.

src/heap.cc

Index: src/heap.cc
diff --git a/src/heap.cc b/src/heap.cc
index 67759e67b63aee8552c827f92e2c68add42d02f2..41eff63148c26d52c21605883a78e328419119f1 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -3813,6 +3813,8 @@ MaybeObject* Heap::CreateCode(const CodeDesc& desc,
   // that are dereferenced during the copy to point directly to the actual heap
   // objects. These pointers can include references to the code object itself,
   // through the self_reference parameter.
+  CHECK(code->IsCode());
+  CHECK(code->relocation_info()->IsByteArray());
   code->CopyFrom(desc);
 
 #ifdef VERIFY_HEAP