RosAlloc verification.

If enabled, RosAlloc verification checks the allocator internal
metadata and invariants to detect bugs, heap corruptions, and race
conditions. Added runtime options for enabling and disabling
it. Enable it for the debug build.

Bug: 9986565
Bug: 12592026
Change-Id: I923742b87805ae839f1549d78d0d492733da6a58
diff --git a/runtime/gc/collector/semi_space.cc b/runtime/gc/collector/semi_space.cc
index 03307f5..0c6a938 100644
--- a/runtime/gc/collector/semi_space.cc
+++ b/runtime/gc/collector/semi_space.cc
@@ -182,6 +182,7 @@
     }
   }
   Locks::mutator_lock_->AssertExclusiveHeld(self_);
+
   TimingLogger::ScopedSplit split("MarkingPhase", &timings_);
   // Need to do this with mutators paused so that somebody doesn't accidentally allocate into the
   // wrong space.