Revert r1380 that is breaking frog.

runtime/vm/object_store.h

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_OBJECT_STORE_H_
 #define VM_OBJECT_STORE_H_
 
 #include "vm/object.h"
 
 namespace dart {
@@ skipping 186 matching lines @@
   }
 
   // Returns head of list of registered libraries.
   RawLibrary* registered_libraries() const { return registered_libraries_; }
   void set_registered_libraries(const Library& value) {
     registered_libraries_ = value.raw();
   }
 
   RawArray* pending_classes() const { return pending_classes_; }
   void set_pending_classes(const Array& value) {
+    ASSERT(!value.IsNull());
     pending_classes_ = value.raw();
   }
 
   RawString* sticky_error() const { return sticky_error_; }
   void set_sticky_error(const String& value) {
     ASSERT(!value.IsNull());
     sticky_error_ = value.raw();
   }
 
   RawBool* true_value() const { return true_value_; }
@@ skipping 63 matching lines @@
   RawObject** to() { return reinterpret_cast<RawObject**>(&empty_context_); }
 
   friend class SnapshotReader;
 
   DISALLOW_COPY_AND_ASSIGN(ObjectStore);
 };
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_STORE_H_