Some fixes for the CC collector.

- Remove a DCHECK in DisableMarkingCheckpoint, which caused
  occasional (false) failures.
- Check the thread-local GetWeakRefAccessEnabled in boxed lambdas weak
  access.
- Add missing BroadcastForNewAllocationRecords and
  BroadcastForNewWeakBoxedLambdas. The lack of the former caused
  occasional deadlocks in the ddmc test.
- Remove the 'ensure system weaks disallowed' calls, which weren't
  useful and dead.

Bug: 12687968
Change-Id: I33850c8d12e6e1a3aed1c2bb18eba263cbab76e8
diff --git a/runtime/gc/heap.h b/runtime/gc/heap.h
index 8bffe5e..d0d0be3 100644
--- a/runtime/gc/heap.h
+++ b/runtime/gc/heap.h
@@ -753,6 +753,10 @@
       SHARED_REQUIRES(Locks::mutator_lock_)
       REQUIRES(!Locks::alloc_tracker_lock_);
 
+  void BroadcastForNewAllocationRecords() const
+      SHARED_REQUIRES(Locks::mutator_lock_)
+      REQUIRES(!Locks::alloc_tracker_lock_);
+
   void DisableGCForShutdown() REQUIRES(!*gc_complete_lock_);
 
   // Create a new alloc space and compact default alloc space to it.