Simple heap trimming.

Change-Id: I8a94b637e64c6b5586db3c41b6e9230e7c8250c8
diff --git a/src/heap.h b/src/heap.h
index ebb1c85..58d7924 100644
--- a/src/heap.h
+++ b/src/heap.h
@@ -218,6 +218,8 @@
   // Pushes a list of cleared references out to the managed heap.
   static void EnqueueClearedReferences(Object** cleared_references);
 
+  static void RequestHeapTrim();
+
   static void RecordAllocationLocked(AllocSpace* space, const Object* object);
   static void RecordImageAllocations(Space* space);