Fix for issue 9871 - Object::empty_array() returns a broken handle.

runtime/vm/object.h

 // Copyright (c) 2012, 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_H_
 #define VM_OBJECT_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
@@ skipping 4816 matching lines @@
   }
 
   void SetLength(intptr_t value) const {
     // This is only safe because we create a new Smi, which does not cause
     // heap allocation.
     raw_ptr()->length_ = Smi::New(value);
   }
 
   HEAP_OBJECT_IMPLEMENTATION(Array, Instance);
   friend class Class;
+  friend class Object;
   friend class String;
 };
 
 
 class ImmutableArray : public Array {
  public:
   static RawImmutableArray* New(intptr_t len, Heap::Space space = Heap::kNew);
 
  private:
   FINAL_HEAP_OBJECT_IMPLEMENTATION(ImmutableArray, Array);
@@ skipping 810 matching lines @@
 
 
 RawObject* MegamorphicCache::GetTargetFunction(const Array& array,
                                                intptr_t index) {
   return array.At((index * kEntryLength) + kTargetFunctionIndex);
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_