Make valgrind happier and stop us leaking so much we can can't run the tests on a device.

Change-Id: Id8f45dde788fd84c10b0b5807b2d12eae529ba5e
diff --git a/src/reference_table.cc b/src/reference_table.cc
index b5c988a..ebdb7bc 100644
--- a/src/reference_table.cc
+++ b/src/reference_table.cc
@@ -29,6 +29,9 @@
   entries_.reserve(initial_size);
 }
 
+ReferenceTable::~ReferenceTable() {
+}
+
 void ReferenceTable::Add(const Object* obj) {
   DCHECK(obj != NULL);
   if (entries_.size() == max_size_) {