Don't overload FreeListElement for become.

runtime/vm/class_table.cc

Index: runtime/vm/class_table.cc
diff --git a/runtime/vm/class_table.cc b/runtime/vm/class_table.cc
index 8cb9fa192a50850752d0ab7c706c4aa1eadfcf4e..b409f80c19050385433664c9a3c1ac948d9aab9b 100644
--- a/runtime/vm/class_table.cc
+++ b/runtime/vm/class_table.cc
@@ -35,6 +35,7 @@ ClassTable::ClassTable()
       table_[i] = vm_class_table->At(i);
     }
     table_[kFreeListElement] = vm_class_table->At(kFreeListElement);
+    table_[kForwardingCorpse] = vm_class_table->At(kForwardingCorpse);
     table_[kDynamicCid] = vm_class_table->At(kDynamicCid);
     table_[kVoidCid] = vm_class_table->At(kVoidCid);
     class_heap_stats_table_ = reinterpret_cast<ClassHeapStats*>(
@@ -218,7 +219,7 @@ void ClassTable::Print() {
     if (!HasValidClassAt(i)) {
       continue;
     }
-    if (i == kFreeListElement) {
+    if (i == kFreeListElement || i == kForwardingCorpse) {

[Cutch, 2016/06/02 14:09:53]

This continue shouldn't be necessary anymore because we can now call Name on
both free list and forwarding corpse classes?

[rmacnak, 2016/06/02 17:57:06]

Done.

       continue;
     }
     cls = At(i);
@@ -395,7 +396,10 @@ ClassHeapStats* ClassTable::PreliminaryStatsAt(intptr_t cid) {
 
 
 ClassHeapStats* ClassTable::StatsWithUpdatedSize(intptr_t cid) {
-  if (!HasValidClassAt(cid) || (cid == kFreeListElement) || (cid == kSmiCid)) {
+  if (!HasValidClassAt(cid) ||
+      (cid == kFreeListElement) ||
+      (cid == kForwardingCorpse) ||
+      (cid == kSmiCid)) {
     return NULL;
   }
   Class& cls = Class::Handle(At(cid));