Remove assumption from the heap verifier that objects occupy a narrow range of the address space.

runtime/vm/scavenger.cc

Index: runtime/vm/scavenger.cc
diff --git a/runtime/vm/scavenger.cc b/runtime/vm/scavenger.cc
index cb028cee155eea76a20424b21849dd8614208eae..fe366b0a4acd29012fda89ab084f74c405eb9e94 100644
--- a/runtime/vm/scavenger.cc
+++ b/runtime/vm/scavenger.cc
@@ -9,6 +9,7 @@
 #include "vm/isolate.h"
 #include "vm/lockers.h"
 #include "vm/object.h"
+#include "vm/object_set.h"
 #include "vm/object_id_ring.h"
 #include "vm/safepoint.h"
 #include "vm/stack_frame.h"
@@ -745,6 +746,11 @@ void Scavenger::VisitObjects(ObjectVisitor* visitor) const {
 }
 
 
+void Scavenger::AddRegionsToObjectSet(ObjectSet* set) const {
+  set->AddRegion(to_->start(), to_->end());
+}
+
+
 RawObject* Scavenger::FindObject(FindObjectVisitor* visitor) const {
   ASSERT(!scavenging_);
   uword cur = FirstObjectStart();