Improve the OOME fragmentation message.

Change-Id: I390d3622f8d572ec7e34ea6dff9e1e0936e81ac1
diff --git a/runtime/gc/allocator/rosalloc.h b/runtime/gc/allocator/rosalloc.h
index fad0dc8..85a8225 100644
--- a/runtime/gc/allocator/rosalloc.h
+++ b/runtime/gc/allocator/rosalloc.h
@@ -590,6 +590,8 @@
 
   // Verify for debugging.
   void Verify() EXCLUSIVE_LOCKS_REQUIRED(Locks::mutator_lock_);
+
+  void LogFragmentationAllocFailure(std::ostream& os, size_t failed_alloc_bytes);
 };
 
 }  // namespace allocator