Fix Harmony sets and maps to allow null as key.

src/heap-inl.h

Index: src/heap-inl.h
diff --git a/src/heap-inl.h b/src/heap-inl.h
index aaf2927f7f941a4f3cb9648a15ef6a7eae05df3b..c065b73daa70354c5652b7775d1f46b671b2d6d4 100644
--- a/src/heap-inl.h
+++ b/src/heap-inl.h
@@ -571,11 +571,11 @@ void ExternalStringTable::Verify() {
 #ifdef DEBUG
   for (int i = 0; i < new_space_strings_.length(); ++i) {
     ASSERT(heap_->InNewSpace(new_space_strings_[i]));
-    ASSERT(new_space_strings_[i] != HEAP->raw_unchecked_null_value());
+    ASSERT(new_space_strings_[i] != HEAP->raw_unchecked_the_hole_value());
   }
   for (int i = 0; i < old_space_strings_.length(); ++i) {
     ASSERT(!heap_->InNewSpace(old_space_strings_[i]));
-    ASSERT(old_space_strings_[i] != HEAP->raw_unchecked_null_value());
+    ASSERT(old_space_strings_[i] != HEAP->raw_unchecked_the_hole_value());
   }
 #endif
 }