Add verification code to dependent code.

src/compiler.cc

Index: src/compiler.cc
diff --git a/src/compiler.cc b/src/compiler.cc
index c6b911feecc8e0d48972e9a57fd046daf84e1421..0ca4212bc77a6296109ece04dfaa4e292177728f 100644
--- a/src/compiler.cc
+++ b/src/compiler.cc
@@ -147,7 +147,9 @@ void CompilationInfo::CommitDependentMaps(Handle<Code> code) {
       group_maps->at(j)->dependent_code()->UpdateToFinishedCode(
           static_cast<DependentCode::DependencyGroup>(i), this, *code);
     }
+#ifndef DEBUG
     dependent_maps_[i] = NULL;  // Zone-allocated, no need to delete.
+#endif
   }
 }
 
@@ -161,8 +163,29 @@ void CompilationInfo::RollbackDependentMaps() {
       group_maps->at(j)->dependent_code()->RemoveCompilationInfo(
           static_cast<DependentCode::DependencyGroup>(i), this);
     }
+#ifndef DEBUG
     dependent_maps_[i] = NULL;  // Zone-allocated, no need to delete.
+#endif
   }
+
+#ifdef DEBUG
+  // Verify that with sequential recompilation, we don't leave any
+  // compilation wrappers behind.
+  if (!FLAG_parallel_recompilation) {
+    for (int i = 0; i < DependentCode::kGroupCount; i++) {
+      ZoneList<Handle<Map> >* group_maps = dependent_maps_[i];
+      if (group_maps == NULL) continue;
+      for (int j = 0; j < group_maps->length(); j++) {
+        DependentCode* dependent_code = group_maps->at(j)->dependent_code();
+        DependentCode::GroupStartIndexes starts(dependent_code);
+        for (int i = 0; i < starts.number_of_entries(); i++) {
+          ASSERT(dependent_code->object_at(i)->IsCode());
+        }
+      }
+      dependent_maps_[i] = NULL;  // Zone-allocated, no need to delete.
+    }
+  }
+#endif  // DEBUG
 }