Move field index into property details, freeing up the value slot of fields.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index e83a32d059d19ee30bbf1a0e4fa27b21ec739452..53aa6e60e456f266a4567884035c52d45f2923c3 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -2497,8 +2497,6 @@ Map* Map::FindLastMatchMap(int verbatim,
     if (details.type() != next_details.type()) break;
     if (details.attributes() != next_details.attributes()) break;
     if (!details.representation().Equals(next_details.representation())) break;
-    ASSERT(!details.IsDeleted());
-    ASSERT(!next_details.IsDeleted());
 
     current = next;
   }