1. Added new flag verify_gc_contains and moved all the asserts that do a

runtime/vm/heap.cc

Index: runtime/vm/heap.cc
diff --git a/runtime/vm/heap.cc b/runtime/vm/heap.cc
index fce8cfee29dffcbfe1c5d2f6604112e8b6e2ac12..c7ce678e19d4a5a890977be5377f5b9db85bcdda 100644
--- a/runtime/vm/heap.cc
+++ b/runtime/vm/heap.cc
@@ -178,6 +178,11 @@ bool Heap::CodeContains(uword addr) const {
 }
 
 
+bool Heap::DataContains(uword addr) const {
+  return old_space_.DataContains(addr);
+}
+
+
 void Heap::VisitObjects(ObjectVisitor* visitor) const {
   new_space_.VisitObjects(visitor);
   old_space_.VisitObjects(visitor);