Add RosAlloc stats dump.

For better understanding of the RosAlloc space.

Bug: 27744947
Bug: 9986565
Change-Id: I02a8028b9728f6862e5e78588a368b8029bb5c1a
diff --git a/runtime/gc/space/rosalloc_space.cc b/runtime/gc/space/rosalloc_space.cc
index 203d3bc..b016095 100644
--- a/runtime/gc/space/rosalloc_space.cc
+++ b/runtime/gc/space/rosalloc_space.cc
@@ -368,6 +368,11 @@
   SetFootprintLimit(footprint_limit);
 }
 
+void RosAllocSpace::DumpStats(std::ostream& os) {
+  ScopedSuspendAll ssa(__FUNCTION__);
+  rosalloc_->DumpStats(os);
+}
+
 }  // namespace space
 
 namespace allocator {