ART: Fix new[] / delete mismatch

The type of the unique_ptr in MarkQueue should be an array type,
as it is holding an array, actually.

Change-Id: If1d05a1d52cd58a373f240f7156fc69b70324298
diff --git a/runtime/gc/collector/concurrent_copying.h b/runtime/gc/collector/concurrent_copying.h
index d740bf2..43f520a 100644
--- a/runtime/gc/collector/concurrent_copying.h
+++ b/runtime/gc/collector/concurrent_copying.h
@@ -129,7 +129,7 @@
   Atomic<size_t> tail_;
 
   size_t size_;
-  std::unique_ptr<Atomic<mirror::Object*>> buf_;
+  std::unique_ptr<Atomic<mirror::Object*>[]> buf_;
 };
 
 class ConcurrentCopying : public GarbageCollector {