Reduced frequency of blocks for concurrent gc

Immediately return for references that are marked before reference
processing without blocking. Soft references are kept in the queue until
the reference processor stops preserving, after which, all marked
references are removed. Finalizer references will still block on get().

Bug: 15471830
Change-Id: I588fcaef40b79ed7c95a4aa7f4fc2e17ee0c288f
diff --git a/runtime/gc/reference_queue.h b/runtime/gc/reference_queue.h
index 4f223e2..1d8cc1a 100644
--- a/runtime/gc/reference_queue.h
+++ b/runtime/gc/reference_queue.h
@@ -65,7 +65,7 @@
   // Walks the reference list marking any references subject to the reference clearing policy.
   // References with a black referent are removed from the list.  References with white referents
   // biased toward saving are blackened and also removed from the list.
-  void PreserveSomeSoftReferences(IsMarkedCallback* preserve_callback, void* arg)
+  void ForwardSoftReferences(IsMarkedCallback* preserve_callback, void* arg)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
   // Unlink the reference list clearing references objects with white referents.  Cleared references
   // registered to a reference queue are scheduled for appending by the heap worker thread.